Magnetic Properties of Matter — Physics STD 11 Science — Question

Read the passage given below and answer the following questions from 1 to 5.
Power is defined as the time rate at which work is done or energy is transferred. The average power of a force is defined as the ratio of the work, W, to the total time t taken
P_av = W/t
The instantaneous power is defined as the limiting value of the average power as time interval approaches zero.
P = dw/dt
The work dW done by a force F for a displacement dr is dW = F.dr. The instantaneous power can also be expressed as
P = F.dr/dt
P = F.v
Where v is the instantaneous velocity when the force is F. Power, like work and energy, is a scalar quantity. Its dimensions are [ML² T^-3]. In the SI, its unit is called a watt (W). The watt is 1 J s^-1. The unit of power is named after James Watt, one of the innovators of the steam engine in the eighteenth century. There is another unit of power, namely the horse-power (hp)
1 hp = 746W
This unit is still used to describe the output of automobiles, motorbikes.

1. The time rate at which work is done or energy is transferred is called as:

1. Energy
2. Force
3. Power
4. None of these

2. Limiting value of power as time interval approaches zero is called as:

1. Average power
2. Instantaneous power
3. Both a and b
4. None of these

3. Power is directly proportional to:

1. Force
2. Velocity
3. Both
4. None of these

4. Define instantaneous power. Give its SI unit and dimensions.

5. 1 horse power is equal to how many watt?

Read the passage given below and answer the following questions from i to v.
If an object moving along the straight line covers equal distances in equal intervals of time, it is said to be in uniform motion along a straight line. Distance and displacement are two quantities that seem to mean the same but are different with different meanings and definitions. Distance is the measure of actual path length travelled by object. It is scalar quantity having SI unit of metre while displacement refers to the shortest distance between initial and final position of object. It is vector quantity. The magnitude of the displacement for a course of motion may be zero but the corresponding path length is not zero. using this data answer following questions.

1. Can path length be zero for motion of body from one point to other point?

1. Yes
2. No

2. For any given motion from point A to B, displacement =10m and distance = 5m. Is it possible?

1. Yes
2. No

3. For rectilinear motion displacement can be

1. Positive only
2. Negative only
3. Can be zero
4. All of the above

4. Define distance and displacement of particle.

5. Write difference between distance and displacement.

A police jeep is chasing a culprit going on a motorbike. The motorbike crosses a turning at a speed of 72km/h. The jeep follows it at a speed of 90km/h, crossing the turning ten seconds later than the bike. Assuming that they travel at constant speeds, how far from the turning will the jeep catch up with the bike?

You are waiting for a train on a railway platform. Your three year old niece is standing on your iron trunk containing the luggage. Why does the trunk not recoil as she jumps off on the platform?

After a good meal at a party you wash your hands and find that you have forgotten to bring your handkerchief. You shake your hands vigorously to remove the water as much as you can. Why is water removed in this process?

The friction coefficient between an athelete's shoes and the ground is 0.90. Suppose a superman wears these shoes and races for 50m. There is no upper limit on his capacity of running at high speeds.

1. Find the minimum time that he will have to take in completing the 50m starting from rest.
2. Suppose he takes exactly this minimum time to complete the 50m, what minimum time will he take to stop?