Wednesday, 22 June 2016

Improvement in Food Resources

Improvement in Food Resources
1. What do we get from cereals, pulses, fruits and vegetables?

Answer

→ Cereals provide us with carbohydrates. Also, they are a rich source of energy.
→ Pulses give us proteins.
→ Fruits and vegetables are a rich source of vitamins and minerals. A small amount of proteins, carbohydrates, and fats are also present in them.


1. How do biotic and abiotic factors affect crop production?

Answer

Biotic factors such as pests, insects and diseases reduce the crop production. A pest causes damage to our crops by feeding. Weeds also reduce crop productivity by competing with the main crop for nutrients and light.
Similarly, abiotic factors such as temperature, wind, rain etc. affect the net crop production. For example droughts and floods have a great impact on crops sometimes, destroying the entire crop.

2. What are the desirable agronomic characteristics for crop improvements?

Answer

The desirable agronomic characteristics for crop improvements are:
→ Tallness and profuse branching in any fodder crop.
→ Dwarfness in cereals.

1. What are macro-nutrients and why are they called macro-nutrients?

Answer

Macro-nutrients are those nutrients which are required in large quantities for growth and development of plants. Since they are required in large quantities, they are known as macro-nutrient. The six macro-nutrients required by plants are nitrogen, phosphorus, potassium, calcium, magnesium, and sulphur.

2. How do plants get nutrients?

Answer

Plants get nutrients from air, water, and soil. Soil is the major source of nutrients. Thirteen of these nutrients are available from soil. The remaining three nutrients (carbon, oxygen, and hydrogen) are obtained from air and water.


1. Compare the use of manure and fertilizers in maintaining soil fertility.

Answer

Manures increase soil fertility by enriching the soil with organic matter and nutrients as it is prepared by the decomposition of animal excreta and plant wastes. On the other hand, fertilizers are mostly inorganic compounds whose excessive use is harmful to the symbiotic micro-organisms living in soil. Their excessive use also reduces soil fertility. Hence, fertilizers are considered good for only short term use.


1. Which of the following conditions will give the most benefits? Why?
(a) Farmers use high-quality seeds, do not adopt irrigation or use fertilizers.
(b) Farmers use ordinary seeds, adopt irrigation and use fertilizer.
(c) Farmers use quality seeds, adopt irrigation, use fertilizer and use crop protection measures.

Answer

(c)Farmers using good quality seeds, adopting irrigation, using fertilizers, and using crop protection measures will derive most benefits.
→ The use of good quality seeds increases the total crop production. If a farmer is using good quality seeds, then a majority of the seeds will germinate properly, and will grow into a healthy plant.
→ Proper irrigation methods improve the water availability to crops.
→ Fertilizers ensure healthy growth and development in plants by providing the essential nutrients such as nitrogen, phosphorus, potassium, etc.
→ Crop protection measures include various methods to control weeds, pests, and infectious agents. If all these necessary measures are taken by a farmer, then the overall production of crops will increase.


1. Why should preventive measures and biological control methods be preferred for protecting crops?

Answer

Preventive measures and biological control methods should be preferred for protecting crops because excessive use of chemicals leads to environmental problems. Biological methods cause harm neither to crop nor to the environment.

2. What factors may be responsible for losses of grains during storage?

Answer

Factors causing loss of grains during storage:
→ Biotic Factors: Insects, rodents, fungi and bacteria etc.
→ Abiotic Factors: Moisture Content and Temprature etc.


1. Which method is commonly used for improving cattle breeds and why?

Answer

Cross Breeding is commonly used for improving cattle breeds.Cross breeding between two good varieties of cattle will produce a new improved variety. For example, the cross between foreign breeds such as Jersey Brown, Swiss and Indian breeds such as Red Sindhi, Sahiwal produces a new variety having qualities of both breeds.


1. Discuss the implications of the following statement:
"It is interesting to note that poultry is India's most efficient converter of low fibre food stuff (which is unfit for human consumption) into highly nutritious animal protein food."

Answer

Poultry in India is the most efficient converter of low fibre food stuff into highly nutritious animal protein food. In poultry farming, domestic fowls are raised to produce eggs and chicken. For this, the fowls are given animal feeds in the form of roughage, which mainly consists of fibres. Thus, by feeding animals a fibre rich diet, the poultry gives highly nutritious food in the form of eggs and chicken.

1. What management practices are common in dairy and poultry farming?

Answer

Common management practices in dairy and poultry farming are:
→ Proper shelter facilities and their regular cleaning.
→ Some basic hygienic conditions such as clean water, nutritious food, etc.
→ Animals are kept in spacious, airy, and ventilated place.
→ Prevention and cure of diseases at the right time is ensured.

2. What are the differences between broilers and layers and in their management?

Answer

Layers are meant for egg production, whereas broilers are meant for poultry meat. Nutritional, environmental, and housing conditions required by broilers are different from those required by egg layers. A broiler chicken, for their proper growth, requires vitamin rich supplements especially vitamin A and K. Also, their diet includes protein rich food and enough fat. They also require extra care and maintenance to increase their survival rate in comparison to egg layers.


1. How are fish obtained?

Answer

Fish can be obtained by two ways:
→ Capture fishing: It is the process of obtaining fish from natural resources.
→ Culture fishery: It is the practice of farming fishes. Farming can be done in both freshwater ecosystem (which includes river water, pond water) and marine ecosystem.

2. What are the desirable characters of bee varieties suitable for honey production?

Answer

Bee varieties having the following desirable characters are suitable for honey production:
→They should yield high quantity of honey.
→ They should not sting much.
→ They should stay in the beehive for long durations.
→ They should breed very well.

1. What are the advantages of composite fish culture?

Answer

The advantages of composite fish culture are:
→ Fish can be grown in crop fields especially paddy.
→ Intensive Fish farming is possible because plenty of water is available during crop seasons.
→ In this system both local and imported fish species can be cultivated.

2. What is pasturage and how is it related to honey production?

Answer

Pasturage is the availability of flowers from which bees collect nectar and pollen. It is related to the production of honey as it determines the taste and quantity of honey.


Excercise

1. Explain any one method of crop production which ensures high yield.

Answer

Inter cropping is a method of crop production which ensures high yield. It is a practice of growing two or more crops simultaneously. in the same field in rows. In inter cropping definite row patterns are followed such as one row of main crop of is followed by two row of intercrop.
In inter cropping there is greater utilisation of the interspaced area, light, nutrients, water and air. As a result productivity per unit area increased.

2. Why are manures and fertilizers used in fields?

Answer

Manures and fertilizers are used in fields to enrich the soil with the required nutrients. Manure helps in enriching the soil with organic matter and nutrients. This improves the fertility and structure of the soil. On the other hand, fertilizers ensure a healthy growth and development in plants. They are a good source of nitrogen, phosphorus, and potassium. To get an optimum yield, it is instructed to use a balanced combination of manures and fertilizers in the so
il.

3. What are the advantages of inter-cropping and crop rotation?

Answer

Inter-cropping and crop rotation both are used to get maximum benefit on limited land. Inter-cropping helps in preventing pests and diseases to spread throughout the field. It also increases soil fertility, whereas crop rotation prevents soil depletion, increases soil fertility, and reduces soil erosion. Both these methods reduce the need for fertilizers. It also helps in controlling weeds and controls the growth of pathogens and pests in crops.

4. What is genetic manipulation? How is it useful in agricultural practices?

Answer

Genetic manipulationis a process where the gene for a particular character is introduced inside the chromosome of a cell. When the gene for a particular character is introduced in a plant cell, a transgenic plant is produced. These transgenic plants exhibit characters governed by the newly introduced gene.
Genetic manipulation is useful in developing varities with Higher yield, Good Quality, Biotic and Abiotic resistance, short maturity period, wider adaptability and desirable agronomic characteristics

5. How do storage grain losses occur?

Answer

There are various biotic and abiotic factors that act on stored grains and result in degradation, poor germinability, discolouration, etc.
Biotic factors include insects or pests that cause direct damage by feeding on seeds. They also deteriorate and contaminate the grain, making it unfit for further consumption.
Abiotic factors such as temperature, light, moisture, etc., also affect the seed. They decrease the germinating ability of the seeds and make them unfit for future use by farmers. Unpredictable occurrence of natural calamities such as droughts and floods also causes destruction of crops.

6. How do good animal husbandry practices benefit farmers?

Answer

Cattle farming is one of the methods of animal husbandry that is most beneficial for farmers. Using this method, better breeds of draught animals can be produced. Such draught animals are engaged in agricultural fields for labour work such as carting, irrigation, tilling, etc.

7. What are the benefits of cattle farming?

Answer

Benefits of cattle farming:
→ Good quality and quantity of milk can be produced.
→ Draught labour animals can be produced for agricultural work.
→ New variety that are resistant to diseases can be produced by crossing two varieties with the desired traits.

8. For increasing production, what is common in poultry, fisheries and bee-keeping?

Answer

The common factor for increasing production in poultry, fisheries, and bee keeping is the proper management techniques that are to be followed. Regular cleaning of farms is of utmost importance. Maintenance of temperature and prevention and cure of diseases is also required to increase the number of animals.

9. How do you differentiate between capture fishing, mariculture and aquaculture?

Answer

→ Capture fishing the method of obtaining fishes from natural resources
→ Mariculture is the culture of marine fishes for commercial use.

→ Aquaculture involves the production of aquatic animals that are of high economic value such as prawns, lobsters, fishes, crabs, etc.

Tuesday, 21 June 2016

Motion

PHYSICS

 Question : 1 - An object has moved through a distance. Can it have zero displacement? If yes, support your answer with an example.

Answer:-
Yes, zero displacement is possible if an object has moved through a distance.

Suppose a ball starts moving from point A and it returns back at same point A, then the distance will be equal to 20 meters while displacement will be zero.
Question : 2 - A farmer moves along the boundary of a square field of side 10 m in 40 s. What will be the magnitude of displacement of the farmer at the end of 2 minutes 20 seconds from his initial position?
Answer:-

Given, side of the square field = 10m
Therefore, perimeter = 10 m x 4 = 40 m
Farmer moves along the boundary in 40s.
Displacement after 2 m 20 s = 2 x 60 s + 20 s = 140 s =?
Since in 40 s farmer moves 40 m

Question : 3 - Which of the following is true for displacement?
(a) It cannot be zero.
(b) Its magnitude is greater than the distance travelled by the object.
Answer: None
Question : 4 - Distinguish between speed and velocity.
Answer:
Speed has only magnitude while velocity has both magnitude and direction.
Question : 5 - Under what condition(s) is the magnitude of average velocity of an object equal to its average speed?
Answer: The magnitude of average velocity of an object will be equal to its average speed in the condition of uniform velocity.
Question : 6 - What does the odometer of an automobile measure?
Answer: In automobiles, odometer is used to measure the distance.
Question : 7 - What does the path of an object look like when it is in uniform motion?
Answer: In the case of uniform motion the path of an object will look like a straight line.

 

Solution of In Text Questions - 2
Question :- 8 - During an experiment, a signal from a spaceship reached the ground station in five minutes. What was the distance of the spaceship from the ground station? The signal travels at the speed of light, that is, 3 × 108 ms-1.
Answer:-

Question : 9 - When will you say a body is in
(i) uniform acceleration?
(ii) non-uniform acceleration?
Answer:
(i) A body is said in uniform acceleration when its motion is along a straight line and its velocity changes by equal magnitude in equal interval of time.
(ii)A body is said in non-uniform acceleration when its motion is along a straight line and its velocity changes by unequal magnitude in equal interval of time.
Question : 10 - A bus decreases its speed from 80 km/h to 60 km/h in 5 s. Find the acceleration of the bus.
Answer:

Question : 11 - A train starting from a railway station and moving with uniform acceleration attains a speed of 40 km/h in 10 minutes. Find its acceleration.
Answer:
Here we have,
Initial velocity, u = 0,
Final velocity, v = 40km/h = 11.11m/s
Time (t) = 10 minute = 60x10=600s
Acceleration (a) =?

Question : 12 - What is the nature of the distance-time graphs for uniform and non-uniform motion of an object?
Answer:
(a) The slope of the distance-time graph for an object in uniform motion is straight line.
(b) The slope of the distance-time graph for an object in non-uniform motion is not a straight line.
Question : 13 - What can you say about the motion of an object whose distance-time graph is a straight line parallel to the time axis?
Answer:
When the slope of distance-time graph is a straight line parallel to time axis, the object is moving with uniform motion.
Question : 14 - What can you say about the motion of an object if its speed-time graph is a straight line parallel to the time axis?
Answer:
When the slope of a speed time graph is a straight line parallel to the time axis, the object is moving with uniform speed.

Solution of In Text Questions - 3

Question : 15 - What is the quantity which is measured by the area occupied below the velocity-time graph?
Answer:-
The quantity of distance is measured by the area occupied below the velocity time graph.
Question :- 16 - A bus starting from rest moves with a uniform acceleration of 0.1 m s-2 for 2 minutes. Find (a)the speed acquired, (b) the distance travelled.
Answer:
Here we have,
Initial velocity (u) = 0
Acceleration (a) = 0.1ms-2
Time (t) = 2 minute = 120 second
(a) The speed acquired:
We know that, v = u + at
v = 0 + 0.1m/s2 x 120 s
v = 120 m/s
Thus, the bus will acquire a speed of 120 m/s after 2 minute with the given acceleration.
(b) The distance travelled:

Question : 17 - A train is travelling at a speed of 90 km/h. Brakes are applied so as to produce a uniform acceleration of – 0.5 m s-2. Find how far the train will go before it is brought to rest.
Answer:
Here,we have,

Question : 18 - A trolley, while going down an inclined plane, has an acceleration of 2 cm s-2. What will be its velocity 3 s after the start?
Answer:
Here we have,
Initial velocity, u = 0
Acceleration (a) = 2cm/s2 = 0.02m/s2
Time (t) = 3s
Therefore, Final velocity, v =?

Question : 19 - A racing car has a uniform acceleration of 4 m s-2. What distance will it cover in 10 s after start?
Answer:
Here we have,
Acceleration, a = 4m/s2
Initial velocity, u =0
Time, t = 10s
Therefore, Distance (s) covered =?

Thus, racing car will cover a distance of 200m after start in 10 s with given acceleration.
Question : 20 - A stone is thrown in a vertically upward direction with a velocity of 5 m s-1. If the acceleration of the stone during its motion is 10 m s-2 in the downward direction, what will be the height attained by the stone and how much time will it take to reach there?
Answer:
Here we have,
Initial velocity (u) = 5m/s
Final velocity (v) =0 (Since from where stone starts falling its velocity will become zero)
Acceleration (a) = -10m/s2
(Since given acceleration is in downward direction, i.e. the velocity of the stone is decreasing, thus acceleration is taken as negative)
Height, i.e. Distance, s =?
Time (t) taken to reach the height =?


Solution of NCERT Exercise (Part 1)
1. An athlete completes one round of a circular track of diameter 200 m in 40 s. What will be the distance covered and the displacement at the end of 2 minutes 20 s?
Answer:-
Here we have,
Diameter = 200 m, therefore, radius = 200m/2 = 100 m
Time of one rotation = 40s
Time after 2m20s = 2 x 60s + 20s = 140s
Distance after 140 s = ?
Displacement after 140s =?
 
(a) Distance after 140s
We know that,distance=velocity ×time
distance=15.7m/s ×140 s = 2198 m
(b) Displacement after 2 m 20 s i.e. in 140 s
Since,rotatin in 40 s=1

Therefore, in 3.5 rotations athlete will be just at the opposite side of the circular track, i.e. at a distance equal to the diameter of the circular track which is equal to 200 m.
Therefore,
Distance covered in 2 m 20 s = 2198 m
And, displacement after 2 m 20 s = 200m
2. Joseph jogs from one end A to the other end B of a straight 300 m road in 2 minutes 30 seconds and then turns around and jogs 100 m back to point C in another 1 minute. What are Joseph’s average speeds and velocities in jogging (a) from A to B and (b) from A to C?
Answer:-

Here we have,
Distance from point A to B = 300 m
Time taken = 2 minute 30 second = 2 x 60 + 30 s = 150 s
Distance from point B to C = 100 m
Time taken = 1 minute = 60 s
(a) Average speed and velocity from point A to B

(b) Average speed and velocity from B to C

Therefore,average velocity=1.66 m/s west
3. Abdul, while driving to school, computes the average speed for his trip to be 20 km/h. On his return trip along the same route, there is less traffic and the average speed is 30 km/h. What is the average speed for Abdul’s trip?
Answer:
Strategy: We need to calculate the time taken in each of the trip. After that, we can calculate the average speed.
Let the distance of the school = s km
Let time to reach the school in first trip = t1
Let time to reach the school in second trip = t2

Therefore, average speed of Adbul = 24 km/h
4. A motorboat starting from rest on a lake accelerates in a straight line at a constant rate of 3.0 m/s2 for 8.0 s. How far does the boat travel during this time?
Answer:
Here we have,
Initial velocity (u) = 0
Acceleration (a) = 3.0m/s2
Time = 8 s
Therefore, distance (s) covered =?

Therefore, boat travel a distance of 96 m in the given time.
5. A driver of a car travelling at 52 km/h applies the brakes and accelerates uniformly in the opposite direction. The car stops in 5 s. Another driver going at 3 km/h in another car applies his brakes slowly and stops in 10 s. On the same graph paper, plot the speed versus time graphs for the two cars. Which of the two cars travelled farther after the brakes were applied?
Answer:
Given for first driver,
 
In the graph, blue slope shows the velocity of the first car and green slope shows the velocity of the second car.
Distance is calculated by the area under the slope of the graph.

Solution of NCERT Exercise (Part 2)

6. Fig 8.11 shows the distance-time graph of three objects A,B and C. Study the graph and answer the following questions:

(a) Which of the three is travelling the fastest?
(b) Are all three ever at the same point on the road?
(c) How far has C travelled when B passes A?
(d) How far has B travelled by the time it passes C?
Answer:-

(a) It is clear from graph that B covers more distance in less time. Therefore, B is the fastest.
(b) All of them never come at the same point at the same time.
(c) According to graph; each small division shows about 0.57 km.
A is passing B at point S which is in line with point P (on the distance axis) and shows about 9.14 km
Thus, at this point C travels about
9.14 – (0.57 x 3.75) km = 9.14 km – 2.1375 km = 7.0025 km ≈ 7 km
Thus, when A passes B, C travels about 7 km.
(d) B passes C at point Q at the distance axis which is ≈ 4km + 0.57km x 2.25 = 5.28 km
Therefore, B travelled about 5.28 km when passes to C.
7. A ball is gently dropped from a height of 20 m. If its velocity increases uniformly at the rate of 10 m/s2, with what velocity will it strike the ground? After what time will it strike the ground?
Answer:-
Here we have,
Initial velocity,u=0
Distance,s=20m
Acceleration,a= 10 m s-2
Final velocity,v=?
Time,t= ?

8. The speed-time graph for a car is shown is Fig. 8.12.

(a) Find how far does the car travel in the first 4 seconds. Shade the area on the graph that represents the distance travelled by the car during the period.
(b) Which part of the graph represents uniform motion of the car?
Answer:

(a) Distance travelled by car in the 4 second
The area under the slope of the speed – time graph gives the distance travelled by an object.
In the given graph
56 full squares and 12 half squares come under the area slope for the time of 4 second.
Total number of squares = 56 + 12/2 = 62 squares
The total area of the squares will give the distance travelled by the car in 4 second.

(b) Part MN of the slope of the graph is straight line parallel to the time axis, thus this potion of graph represents uniform motion of car.
9. State which of the following situations are possible and give an example for each of these:
(a) An object with a constant acceleration but with zero velocity
(b) An object moving in a certain direction with an acceleration in the perpendicular direction.
Answer:
(a) The term acceleration implies that the velocity of the object is changing; inspite of that constant acceleration with zero velocity is impossible. When an object is thrown in upward direction, at the maximum height the velocity of the object becomes zero but still in that condition a constant acceleration due to gravity is working.
(b) Object moving in a certain direction with an acceleration in perpendicular direction is possible; in case of circular motion. When an object moves on a circular path, its direction is along the tangent of the circle but acceleration is towards the radius of the circle. We know, that a tangent always makes a right angle with the radius; so when an object is in circular motion, the acceleration and velocity are in mutually perpendicular direction.
10. An artificial satellite is moving in a circular orbit of radius 42250 km. Calculate its speed if it takes 24 hours to revolve around the earth.
Answer:
Here we have,
Radius, r = 42250km
Time, t = 24 hours
Speed =?