Extended · Practice questions · Gravitational PE

Banked by height.

Six original Cambridge-style questions on calculating change in gravitational potential energy, using the vertical height, and converting between gravitational and kinetic stores.

Original questions All questions on this page are original work, written in the Cambridge IGCSE style. They are not from past papers. They test the same concepts and skills the syllabus rewards.

Watch the height

ΔPE = mgΔh.

Vertical height only: on a slope, use the rise, not the slope length.
Units: mass in kg, g about 9.8 N/kg (or 10 if told), energy in J.
On falling: mgΔh becomes ½mv².

[2 marks]

Write the equation for the change in gravitational potential energy, and state what each symbol represents.

ΔPE = mgΔh. ✓
m = mass (kg), g = gravitational field strength (N/kg), Δh = change in height (m). ✓

Calculation

[2 marks]

A 5.0 kg mass is raised vertically by 3.0 m. Using g = 9.8 N/kg, calculate the gain in gravitational potential energy.

ΔPE = mgΔh = 5.0 × 9.8 × 3.0

147 J

Calculation

[2 marks]

A 0.40 kg book is lifted onto a shelf 1.5 m above the floor. Using g = 10 N/kg, calculate the gain in gravitational potential energy.

ΔPE = 0.40 × 10 × 1.5

6.0 J

Analysis

[2 marks]

A box is pushed up a long sloping ramp to a raised platform. Explain which distance must be used to find the gain in gravitational potential energy.

Use the vertical height gained, not the length along the ramp. ✓
Only the vertical rise changes the gravitational potential energy. ✓

Calculation

[3 marks]

A 2.0 kg mass falls from rest through a height of 5.0 m. Using g = 9.8 N/kg and ignoring air resistance, calculate its speed just before it lands.

ΔPE = mgΔh = 2.0 × 9.8 × 5.0 = 98 J ½mv² = 98 → v² = 98 ÷ 1.0 = 98 v = √98

v ≈ 9.9 m/s

Calculation

[2 marks]

Lifting a 4.0 kg load gives it 240 J of gravitational potential energy. Using g = 10 N/kg, calculate the height it was raised.

240 = 4.0 × 10 × h h = 240 ÷ 40

h = 6.0 m