Advertisements
Advertisements
Question
It takes 20 s for a girl A to climb up the stairs while girl B takes 15 s for the same job. Compare the power spent by then.
Solution
Power = `"Work done"/"Time taken "` = `"Energy" /"Time"`
= `"Power of A "/ "Power of B"` = `(" Energy "/ t_1 )/("Energy "/ t_2)`
= `1/t_1` ' `t_2/1` =`15/20`
= `3/4` = 3 : 4
APPEARS IN
RELATED QUESTIONS
A body is moving unidirectionally under the influence of a source of constant power. Its displacement in time t is proportional to ______.
Match the following
| column A | Column B |
| A stone at a height | power |
| A Moving ball | joule |
| Energy | work done in 1 s |
| Power | potential energy |
| Watt | kinetic energy |
Two coolies A and B do some work in time 1 minute and 2 minute respectively. The power spent is
A pump raises water by spending 4×105J of energy in 10s. Find the power of the pump.
Choose one or more correct alternatives.
Power is a measure of the ______.
- The rapidity with which work is done.
- Amount of energy required to perform the work.
- The slowness with which work is performed.
- Length of time.
Arrive at an expression for power and velocity. Give some examples for the same.
A ball with a velocity of 5 ms−1 impinges at an angle of 60˚ with the vertical on a smooth horizontal plane. If the coefficient of restitution is 0.5, find the velocity and direction after the impact.
Water falls from a height of 60 m at the rate of 15 kg/s to operate a turbine. The losses due to frictional force are 10% of the input energy. How much power is generated by the turbine? (g = 10m/s2)
Calculate the power spent by a crane while lifting a load of mass 2000 kg, at velocity of 1.5 ms-1. (g = 10 ms-2)
Name the quantity which is measured in kW.
