Power

Q.

1 watt is defined as:

1. Power of an agent, which does work at the rate of 1 joule/second

2. Power of an agent, which does work at the rate of 1 joule-second

3. 1 joule of work done in an hour

4. All of these

Q.

If power is increased by 50 % and work done is constant, then the time taken is reduced by:

1. 66.66 %

2. 33.33 %

3. 50 %

4. remains constant

Q.

In a hydroelectric power plant, waterfalls at a rate of 1000 kg/s from a height of 100 m. Assuming that 50% of the energy of falling water is converted into electrical energy, calculate the power generated per second.$(takeg=9.8m{s}^{-2})$

1. 380000 W

2. 200000 W

3. 195000 W

4. 490000 W

Q.

In a hydroelectric power plant, moving water is used for driving the wheels of a turbine to generate electricity. If the change in kinetic energy of turbine is 1200 J in 2 minutes then the power generated is

1. 10 W

2. 200 W

3. 20 W

4. 100 W

Q.

If the work done on a body at two instances i.e., at $\text{20 s}$ and $\text{40 s}$ is same, then what is the ratio of the power?

1. 2:1

2. 1:2

3. 1:4

4. 4:1

Q.

The work done by the heart to beat one time is 1.2 J. If it beats 72 times in 1 minute, calculate the power of heart.

1. 1.6 watt

2. 1.44 watt

3. 0 watt

4. 1.2 watt

Q.

A car accelerates from rest to speed of 100 m/s in 10 seconds. If the mass of the car is 50 kg, then power developed by the engine is:

1. 35 KW

2. 25 KW

3. 20 KW

4. 30 KW

Q.

The rate of doing work or rate at which energy is transferred is known as:

1. Momentum

2. Power

3. Force

4. Velocity

Q.

An electric bulb of rating 50 W is used for 8 hours in one day. Find the number of units of energy used by the electric bulb.

1. 0.4 unit

2. 200 unit

3. 0.6 unit

4. 400 unit

Q.

A skydiver weighing 60 kg moves through a distance of 40 m upwards in 2 seconds. The power spent by the skydiver due to its weight (in Watt) is ___ . $Takeg=9.8m/s^2$