Question
The table shows the work done and the time taken by four machines.
Which machine is the most powerful?
| work done / kJ | time taken / s |
A | 100 | 10 |
B | 100 | 20 |
C | 200 | 10 |
D | 200 | 20 |
Answer/Explanation
Ans: C
Question
What is the unit of power?
joule
newton
pascal
watt
Answer/Explanation
Ans: D
Question
An object is lifted vertically by a motor.
In which example is the power produced the greatest?
A lifting it a shorter distance in a longer time
B lifting it the same distance in a longer time
C lifting it a shorter distance in the same time
D lifting it the same distance in a shorter time
Answer/Explanation
Ans: D
Question
A man can either take an escalator or a lift to travel up between two floors in a hotel.
The escalator takes 20 seconds to carry the man between the two floors. The useful work done against gravity is W. The useful power developed is P.
The lift takes 30 seconds to carry the same man between the same two floors.
How much useful work against gravity is done by the lift, and how much useful power is developed by the lift?
| useful work done against gravity by lift | useful power developed by lift |
A | more than W | less than P |
B | more than W | P |
C | W | less than P |
D | W | P |
Answer/Explanation
Ans: C
Question
The engine of a motor vehicle develops a large amount of power.
Which statement is correct?
The driving force acting on the vehicle must be large.
The engine must have a very large volume.
The engine must transfer large amounts of energy each second.
The vehicle must be very fast.
Answer/Explanation
Ans: C