Gravitational Potential Energy
Answers
Why is it a ‘potential’ energy? stored energy .....................................................................................................
[1]
What is the symbol for gravitational potential energy in your syllabus? Ep ........................................................
[1]
What are the units of gravitational potential energy? joules .............................................................................
[2]
What is the equation for gravitational potential energy? (use symbols)
Ep = m g h............................................................................................................................................................
[1]
…what do the symbols mean? (include units)

m is mass (kg) ..........................................................................................................................................

g is gravitational field strength (N/kg) ....................................................................................................

h is height (m) .........................................................................................................................................
[6]
How much gravitational potential energy does each of the following have? (1 mark is for showing your working)
(Assume g = 9.8 N/kg) equation; answer; units;

a netball (400 g) hits the hoop (3.05 m)
Ep
=m g h
= 0.4 x 9.8 x 3.05

[3]
Answer 171500 J (171.5 kJ; 172 KJ)
[3]
Answer 0.0132 J (0.0132349 J) ......
[3]
a bar-headed goose (2.5 kg) migrating at 7 km above sea level
Ep
=m g h
= 2.5 x 9.8 x 7000

Answer 11.956 J (12; 12.0; 11.96;)
a glass marble (18.5 g) on a desk (73 cm)
Ep
=m g h
= 0.0185 x 9.8 x 0.073
A wren (10 g) standing on a branch has a gravitational potential energy of 0.34 J. How high is the branch?
Ep
=m g h
h
= Ep / (m g)
= 0.34 / (0.01 x 9.8)
= 0.34 / 0.098
Answer 3.47 m (3.469387755.. m)
[3]
A Boeing 747 cruising at 9 km above sea level has a gravitational potential energy of 39487 MJ. What is its mass?
Ep
=m g h
m
= Ep / (h g)
= 39487000000 / (9000 x 9.8)
= 39487000000 / 88200
Answer 447700 kg (447698.4127) .
[3]
The ruby-throated hummingbird has a mass of 3 g. What is its weight? 0.0294 N...........................................
[2]
A protester weighing 600 N climbs on top of Big Ben (96 m). What is their gravitational potential energy?
Ep
=m g h
= 600 x 96
Answer 57600 J (57.6 kJ)................
[3]