Course: Combined and Separate | Use g = 9.8 N/kg. Find each scene on YouTube, watch it, then answer the questions. Write your answers on paper first, then tap Show answer.
Equations you’ll need: s = vt · a = Δv ÷ t · F = ma · W = mg · F = ke · p = mv · W = Fs · KE = ½mv² · v² − u² = 2as · F = mΔv ÷ Δt (Separate)
1. The Incredibles – Mr Incredible stops the train
🎬 The scene: A train heads for a broken bridge and Mr Incredible stands on the track to stop it with his bare hands.
Q1 (F) What is momentum, and what are its units?
Show answer
Momentum = mass × velocity (p = mv). Units: kg m/s.
Q2 (F/H) The train has a mass of 40 000 kg and travels at 20 m/s. Calculate its momentum.
Show answer
p = 40 000 × 20 = 800 000 kg m/s
Q3 (H, Separate) He stops it in 5 s. Calculate the force needed. Real or fake: what would really happen to his feet?
Show answer
F = Δp ÷ t = 800 000 ÷ 5 = 160 000 N. Even if he were strong enough, he’d need that much friction between his feet and the ground – he’d just slide along the track. (The film cleverly shows his feet ripping up the rails!)
2. Spider-Man 2 – stopping the train with webs
🎬 The scene: Spider-Man fires webs at the buildings on either side to stop a runaway train full of passengers. (12A: action.)
Q1 (F) Name two forces acting to slow the train down.
Show answer
Any two: tension in the webs, friction (brakes and Spider-Man’s feet), air resistance.
Q2 (F/H) A web has a spring constant of 50 000 N/m and stretches by 4 m. Calculate the force it exerts.
Show answer
F = ke = 50 000 × 4 = 200 000 N
Q3 (H) The train has a mass of 50 000 kg. Calculate its deceleration, then how far it travels while stopping from 20 m/s.
Show answer
a = F ÷ m = 200 000 ÷ 50 000 = 4 m/s². Using v² − u² = 2as: 0 − 20² = 2 × (−4) × s, so s = 400 ÷ 8 = 50 m.
3. WALL-E – flying with a fire extinguisher
🎬 The scene: Outside the spaceship, WALL-E uses a fire extinguisher to fly through space and dance with EVE.
Q1 (F) Use Newton’s third law to explain how the fire extinguisher pushes WALL-E forward.
Show answer
The extinguisher pushes the gas backwards. The gas pushes the extinguisher (and WALL-E) forwards with an equal and opposite force.
Q2 (F/H) When WALL-E stops spraying, he keeps drifting at a steady speed. Explain why.
Show answer
In space there is no air resistance or friction, so there is no resultant force. By Newton’s first law, he carries on at a constant velocity.
Q3 (H, Separate) WALL-E (100 kg) starts at rest and sprays 0.5 kg of gas backwards at 20 m/s. Use conservation of momentum to find his speed.
Show answer
Total momentum stays zero. Gas: 0.5 × 20 = 10 kg m/s backwards, so WALL-E has 10 kg m/s forwards. v = 10 ÷ 100 = 0.1 m/s
4. Zootopia – Flash the sloth
🎬 The scene: Judy and Nick visit the DMV, where Flash the sloth works at an incredibly slow pace.
Q1 (F) Write the equation linking distance, speed and time.
Show answer
distance = speed × time (s = vt)
Q2 (F/H) Flash moves his hand 2 m in 50 s. Calculate his speed.
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v = 2 ÷ 50 = 0.04 m/s
Q3 (H) At the end of the film, Flash is caught speeding: he covers 100 m in 2.5 s. Calculate his speed. How many times faster is this than in Q2?
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v = 100 ÷ 2.5 = 40 m/s (about 90 mph). 40 ÷ 0.04 = 1000 times faster!
5. Finding Nemo – riding the East Australian Current
🎬 The scene: Marlin and Dory ride the fast-flowing East Australian Current with Crush and the sea turtles.
Q1 (F) What is the difference between speed and velocity?
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Speed is a scalar (size only). Velocity is a vector – it has size and direction.
Q2 (F/H) Marlin swims at 1 m/s in a current flowing at 3 m/s. What is his resultant velocity if he swims (a) with the current, (b) against it?
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(a) 3 + 1 = 4 m/s with the current. (b) 3 − 1 = 2 m/s in the direction of the current – he still goes backwards!
Q3 (H) Marlin swims at 4 m/s straight across a current flowing at 3 m/s. Calculate his resultant speed.
Show answer
The velocities are at right angles, so use Pythagoras: √(4² + 3²) = √25 = 5 m/s. (You could also find this with a scale drawing.)
6. Mary Poppins – arriving by umbrella
🎬 The scene: The wind blows the queue of nannies away, and Mary Poppins floats gently down with her umbrella (1964 film).
Q1 (F) Name the two vertical forces on Mary as she floats down.
Show answer
Weight (downwards) and air resistance (upwards).
Q2 (F/H) She falls at a slow, steady speed. What does this tell you about the forces? What is this speed called?
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The forces are balanced – the resultant force is zero. This steady speed is her terminal velocity.
Q3 (H) Real or fake? Mary’s mass is 60 kg. Calculate her weight, and the air resistance at terminal velocity. Why couldn’t a real umbrella do this?
Show answer
W = mg = 60 × 9.8 = 588 N, so air resistance = 588 N. An umbrella’s area is far too small to give that much air resistance at a gentle speed – a parachute is many times bigger. Fake!
7. Wallace & Gromit: The Wrong Trousers – the train chase
🎬 The scene: Gromit chases Feathers McGraw on the model train, laying the track in front of himself as he goes.
Q1 (F) When Gromit’s train moves at a steady speed in a straight line, what can you say about the forces on it?
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They are balanced: the driving force equals the friction and air resistance, so the resultant force is zero.
Q2 (F/H) The toy train speeds up from 0 to 3 m/s in 6 s. Calculate its acceleration.
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a = Δv ÷ t = 3 ÷ 6 = 0.5 m/s²
Q3 (H) It then travels at 3 m/s for 10 s. Sketch the velocity–time graph and use the area under it to find the total distance.
Show answer
Triangle: ½ × 6 × 3 = 9 m. Rectangle: 10 × 3 = 30 m. Total = 39 m
8. Toy Story – the rocket ride to the truck
🎬 The scene: RC’s batteries run out, so Woody lights the rocket strapped to Buzz and they blast off after the moving van.
Q1 (F) For the rocket to accelerate upwards, how must the thrust compare with the weight?
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The thrust must be bigger than the weight (plus air resistance).
Q2 (F/H) The rocket, Woody and Buzz have a weight of 3 N. The thrust is 12 N. Calculate the resultant force.
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12 − 3 = 9 N upwards
Q3 (H) Their total mass is 0.3 kg. Calculate their acceleration.
Show answer
a = F ÷ m = 9 ÷ 0.3 = 30 m/s² – about three times the acceleration due to gravity!
9. Cars – “Turn right to go left” on the dirt track
🎬 The scene: Lightning McQueen races Doc Hudson on a dirt track and skids off the corner into the cactus patch.
Q1 (F) Why does Lightning McQueen skid off the road on the dirt corner?
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Loose dirt gives much less friction (grip) than tarmac, so there isn’t enough force to turn the car at that speed.
Q2 (F/H) Stopping distance = thinking distance + braking distance. Give two things that increase braking distance.
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Any two: higher speed, wet or icy (or loose) road, worn tyres, worn brakes, a heavier vehicle.
Q3 (H) A 1500 kg car brakes from 20 m/s with a braking force of 6000 N. Use energy to find its braking distance.
Show answer
KE = ½ × 1500 × 20² = 300 000 J. Work done by brakes = KE, so F × s = 300 000, giving s = 300 000 ÷ 6000 = 50 m.
10. Kung Fu Panda – Po vs Tai Lung
🎬 The scene: In the final battle, Tai Lung’s attacks bounce right off Po’s squishy belly.
Q1 (F) Po’s belly squashes and then springs back to its shape. What kind of deformation is this?
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Elastic deformation – it returns to its original shape when the force is removed.
Q2 (F/H) Po’s belly has a spring constant of 2000 N/m and is squashed by 0.15 m. Calculate the force.
Show answer
F = ke = 2000 × 0.15 = 300 N
Q3 (H, Separate) Tai Lung (80 kg) hits Po at 10 m/s and bounces straight back at 10 m/s. The collision lasts 0.2 s. Calculate the change in momentum and the average force.
Show answer
Change in velocity = 10 − (−10) = 20 m/s. Δp = 80 × 20 = 1600 kg m/s. F = Δp ÷ t = 1600 ÷ 0.2 = 8000 N.
Teachers: the buttons open a YouTube search, so you can pick whichever upload is currently available. Please watch the clip through before showing it to a class.
