En anglais

Swapping height for speed

Science · Energy · ages 15-16

Name ______________________ Date ____________

A 0.2 kg ball is 1.8 m above a chosen zero height. Using g = 10 N/kg, what is its gravitational potential energy in J?
Answer: ______________
What is the kinetic energy equation?
- Half m v squared
- Mass times speed
- Mass times g times height
At fixed mass, doubling speed only doubles kinetic energy.
Circle one: True False
A 5 kg box rises 2 m (g = 10 N/kg). What is its gain in gravitational store?
- 10 J
- 20 J
- 100 J
A 2 kg mass moves at 3 m/s. What is its kinetic store in J?
Answer: ______________
A 0.2 kg ball drops from rest through 1.8 m. Ignore air resistance and other transfers. Which relation holds just before impact? KE means kinetic energy; GPE means gravitational potential energy.
- KE + GPE disappears
- Loss in GPE = gain in KE
- Loss in KE = gain in GPE
A ball is launched straight up at 6 m/s. Ignore air resistance and use g = 10 N/kg. Which calculation finds its maximum rise above launch height?
- Multiply launch speed by mass and gravitational field strength
- Equate m g h to the launch kinetic store
- Divide launch speed by gravitational field strength twice
A 0.5 kg ball lands with 16 J of kinetic energy. What is its landing speed in m/s?
Answer: ______________

Answer key

For grown-ups. Fold this page away before handing over the rest.

3.6 · 0.2 times 10 times 1.8 = 3.6 J.
Half m v squared · Kinetic energy = half times mass times speed squared.
False · Speed is squared, so doubling speed gives four times the kinetic energy.
100 J · 5 times 10 times 2 = 100 J.
9 · Half times 2 times 3 squared = 9 J.
Loss in GPE = gain in KE · Under these ideal conditions, the gravitational potential energy lost equals the kinetic energy gained.
Equate m g h to the launch kinetic store · At the top its speed is zero. Set mgh = 0.5m × 6²; mass cancels, giving h = 36 ÷ 20 = 1.8 m.
8 · Half times 0.5 times v squared = 16 gives v squared = 64, so v = 8.