Average and Instaneous Power

Q. What is the average powered delived to a pot of mass m, in lifting it to a height 'h' in a time t?

1. $\frac{mgh}{t}$
2. $\frac{mgh}{2t}$
3. $\frac{2mgh}{t}$
4. $\frac{mg}{t}$

Q.

A 12 HP motor has to be operated 8 hours/day. How much will it cost at the rate of 50 paisa/kWh in 10 days

1. Rs. 358/-

2. Rs. 375/-

3. Rs. 350/-

4. Rs. 397/-

Q.

A body of mass $m$ accelerates uniformly from rest to $v_1$ in time $t_1$. As a function of time $t$, the instantaneous power delivered to the body is [2004 AIEEE]

1. 

2. 

3. 

4. 

Q.

The power of a pump, which can pump 200kg of water to a height of 200m in 10sec is ($g=10m/s^{-2}$)

1. 400 kW

2. 960 kW

3. 40 kW

4. 80 kW

Q.

A box is moved along a straight line by a machine delivering constant power. The distance moved by the body in time t is proportional to

1. $t^{\frac{1}{2}}$

2. $t^{\frac{3}{4}}$

3. $t^{\frac{3}{2}}$

4. $t^2$

Q.

A body of mass m accelerates uniformly from rest to velocity $v_1$ in time $t_1$. The instantaneous power delivered to the body as a function of time t is

1. $\frac{m{v}_1^2{t}^2}{t_1^2}$

2. $\frac{m{v}_1^{2}t}{t_1^2}$

3. $\frac{m{v}_1{t}^2}{t_1}$

4. $\frac{m{v}_{1}t}{t_1}$

Q.

A truck moving on a smooth horizontal surface with a uniform speed u is carrying stone-dust. If a mass $\Delta m$ of the stone-dust leaks from the truck in a time $\Delta t$, the force needed to keep the truck moving at its uniform speed is

1. $u\frac{\Delta m}{\Delta t}$

2. $\Delta m\frac{du}{dt}$

3. $u\frac{\Delta m}{\Delta t}+\left(\Delta m\right)\frac{du}{dt}$

4. zero

Q.

In a hydroelectric power station, the height of the dam is 10 m. How many kg of water must fall per second on the blades of a turbine in order to generate 1 MW of electrical power? Take $g=10m{s}^{-2}$.

1. ${10}^{4}kg{s}^{-1}$

2. ${10}^{5}kg{s}^{-1}$

3. ${10}^{6}kg{s}^{-1}$

4. ${10}^{3}kg{s}^{-1}$

Q. Instantaneous power can be equal to average power.

1. False
2. True

Q. Instantaneous power can be equal to average power.

1. False
2. True