Question
At time = 0, a cannonball is stationary inside a cannon. The cannonball is then fired from the cannon.
At time = t, the cannonball moves forwards and the cannon moves backwards.
What happens to the total kinetic energy and the total momentum of the cannon and the cannonball between time = 0 and time = t?
Answer/Explanation
Ans:
B
This question is about four methods used to produce electrical energy.
Which method has a correct description?
| method | energy source is renewable | emits carbon dioxide |
A | a hydroelectric power station | yes | no |
B | a coal-fired power station | no | no |
C | a wind turbine | no | yes |
D | a nuclear power station | yes | yes |
Answer/Explanation
Ans: A
Question
The power input to an electric motor is 400 W. The efficiency of the motor is 85%.
How much power is wasted?
A 60 W
B 85 W
C 340 W
D 470 W
Answer/Explanation
Ans: A
Question
Which row describes an advantage and a disadvantage of wind turbines?
|
advantage |
disadvantage |
|
|
A |
no fuel needed |
harmful gases released |
|
B |
variable supply |
fuel needed |
|
C |
no harmful gases released |
variable supply |
|
D |
constant supply |
noisy |
Answer/Explanation
Ans: CQuestion
An electric motor provides 900 J of useful output energy. The efficiency of the motor is 60 %.
How much electrical energy is supplied to the motor?
A 15 J
B 540 J
C 1500 J
D 5400 J
Answer/Explanation
Ans: C