WorksheetsEnergy, Work Done, Power and Efficiency - Physics Test C8
Total questions: 25
Worksheet time: 42mins
Rank in order, from largest to smallest, the gravitational potential energies of the balls.
1 > 2 = 4 > 3
1 > 2 > 3 > 4
3 > 2 = 4 > 1
3 > 2 > 4 > 1
Two identical marbles roll down two differemt hills. One rolls down a steeper hill, and the other down a less steep hill. Both hills have the same height. How do you compare the change in Gravitational Potential Enrgy (G.P.E.) for the marbles?
Smaller change in G.P.E. for the steeper hill
Bigger change in G.P.E. for the less steep hill
Same change in G.P.E. for both hills
Can’t say without knowing the mass of the marble
A small child slides down each of the four frictionless slides in the picture. All slides A to D have the SAME HEIGHT. Rank her speeds at the bottom of each slide.
vD > vA > vB > vC
vD > vA = vB > vC
vC > vA > vB > vD
vA = vB = vC = vD
What is the equation used to calculate Kinetic Energy?
K = m . v2
K = m . v
K = 1/2 . m . v2
K = 1/2 . (m . v)2
What is the equation used to calculate Gravitational Potential Energy?
Ug = m . g . h
Ug = m . g
Ug = 1/2 . k . x2
Ug = m . v2
What is the equation used to calculate Work?
W = m . v
W = F . d
W = F / d
W = m . v2
What is stated by the Law of Conservation of Energy?
Energy cannot be created or destroyed, but it can change from one form to another.
The energy of a system will increase over tiime.
The energy of a system will decrease over time.
Energy is only conserved in the absence of friction.
The picture shows a skier taking part in a downhill race.
Her mass, including her equipment, is 75 kg. In the ski race, the total vertical change in height is 880 m.
Calculate the decrease in gravitational potential energy of the skier.
(Use g = 10 N/kg)
750 J
660,000 J
66,000 J
33,000 J
A man lifts three boxes together from the ground on to a shelf that is 1.5 m above the ground. The weight of the boxes is 300 N and the man takes 2.0 s to lift them.
How muck power does the man produce to lift the boxes?
75 W
225 W
300 W
900 W
A skier walks from the bottom of a ski slope to the top and gains 10000J of gravitational potential energy. She skis down the slope. At the bottom of the slope, her kinetic energy is 2000J. How much energy is dissipated in overcoming friction and air resistance as the skier moves down the slope?
2000J
8000J
10 000J
12 000J
A ball is dropped on to a hard surface and bounces. It does not bounce all the way back to where it started, and so has not regained all of its original gravitational potential energy. Which statement accounts for the loss of gravitational potential energy?
Energy was destroyed as the ball hit the ground.
Energy was destroyed as the ball travelled through the air.
The chemical energy and elastic energy of the ball have increased.
The internal (heat) energy of the ball and its surroundings has increased.
A cyclist travels down a hill from rest at point X, without pedalling. The cyclist applies his brakes and the cycle stops at point Y. Which energy changes have taken place between X and Y?
gravitational potential → kinetic → thermal (heat)
gravitational potential → thermal (heat) → kinetic
kinetic → gravitational potential → thermal (heat)
kinetic → thermal (heat) → gravitational potential
A certain machine is very efficient. What does this mean?
It produces a large amount of power.
It uses very little energy.
It wastes very little energy.
It works very quickly.
The diagram shows a hydroelectric system. What are the main energy changes taking place?
chemical energy → kinetic energy → electrical energy
electrical energy → gravitational energy → kinetic energy
gravitational energy → kinetic energy → electrical energy
kinetic energy → electrical energy → gravitational energy
A lorry of mass 4000kg is travelling at a speed of 4.0m/s. A car has a mass of 1000kg. The kinetic energy of the car is equal to the kinetic energy of the lorry. What is the speed of the car?
2.0 m/s
4.0m/s
8.0m/s
16.0m/s
The diagram shows the energy used by a modern lamp. Which expression gives the efficiency of the lamp?
(12/60) x 100%
(12/48) x 100%
(48/60) x 100%
(48/12) x 100%
What is the work output of a machine that has a work input of 2,800 Joules and an efficiency of 90%?
25200 J
2520 J
0.0082J
If there is no friction on this track, at which point would the coaster have the most kinetic energy?
A
B
C
D
Four different children run up the same set of stairs. For which child is the useful power to climb the stairs the GREATEST?
Child A
Child B
Child C
Child D
A 70 kg student travels from the first floor to the fourth floor of a school (a
height of 25 m).
a) What total work did she do to climb the stairs?
b) How long would this trip last if the student produced 250 W of
power?
A van of mass 1500 kg is travelling at 20 m/s.
a) Calculate its kinetic energy.
b) If its speed doubles, by how much does its kinetic energy
increase?
A stone of 800 g is resting at the top of a mountain. The stone stores 4000 J
of gravitational potential energy. How tall is the mountain?
A child of mass 40 kg is sliding down a slide. At the very bottom of the
slide, just before he hits the ground, he reaches a speed of 8 m/s.
a) What is the kinetic energy of the child at the bottom of the slide?
b) What was his gravitational potential energy at the top of the
slide? (Ignore friction and air resistance).
c) How tall is the slide?
An archer fires an arrow of mass 0.05 kg vertically upwards. If the stone has
an initial kinetic energy of 45 J, how far will it travel before it falls back?
