Grade 6 · Science · Unit 3 of 6
Newton's Laws
Three laws of motion
What your child practises
Inertia (1st law), force = mass × acceleration (2nd law) and action–reaction pairs (3rd law), with everyday examples and a few simple calculations.
NWT Curriculum learning standard: Newton's three laws of motion
Sample questions
A taste of this unit. In the app, questions change every time and get easier or harder to match your child.
Question 1
A bus stops suddenly and the riders lurch forward. Why?
🚌- The bus pushes them forward
- The bus floor pulls them forward
- Gravity pulls them forward
- Their bodies keep moving forward because of inertia
Their bodies keep moving forward because of inertia
Hint: The bus stopped, but nothing stopped the riders yet. They keep going the way they were moving.
Question 2
Which of Newton's laws does each example show? Tap an item, then tap its basket.
Sort into: 1️⃣ 1st law: inertia · 2️⃣ 2nd law: F = m × a · 3️⃣ 3rd law: action and reaction
- ⚾A harder throw makes a ball go faster
- 🚚A loaded truck needs more force to speed up than a bike
- 🏊A swimmer pushes water back to move forward
- 🚌Riders lurch forward when a bus brakes hard
- ⚽A ball sits still until someone kicks it
- 🚀A rocket pushes gas down and the gas pushes it up
1️⃣ 1st law: inertia: Riders lurch forward when a bus brakes hard, A ball sits still until someone kicks it · 2️⃣ 2nd law: F = m × a: A harder throw makes a ball go faster, A loaded truck needs more force to speed up than a bike · 3️⃣ 3rd law: action and reaction: A swimmer pushes water back to move forward, A rocket pushes gas down and the gas pushes it up
Hint: 1st law: things keep doing what they're doing (inertia). 2nd law: more force or less mass means more acceleration. 3rd law: every push has an equal push back.
Question 3
How does a rocket lift off?
🚀- Its wings lift it like a plane
- It pushes hot gases down, and the gases push the rocket up
- Gravity pulls it upward
- It pushes against the air above it
It pushes hot gases down, and the gases push the rocket up
Hint: That's Newton's third law: action (gas pushed down) and reaction (rocket pushed up). It even works in space, where there's no air.
Question 4
A 15 kg wagon speeds up at 6 m/s². What net force is acting on it?
F = m × a
answer boxN
90 N
Hint: Newton's second law: force = mass × acceleration. Multiply the mass in kilograms by the acceleration.
Question 5
Far out in space, a probe's engines shut off. What happens to the probe?
🛰️- It starts spinning in circles
- It keeps moving in a straight line at the same speed
- It slowly comes to a stop
- It falls straight down
It keeps moving in a straight line at the same speed
Hint: With no friction or air to slow it, nothing changes its motion. That's Newton's first law.
Question 6
A swimmer pushes off the pool wall. Which force moves the swimmer forward?
🏊- the wall pushing back on the swimmer
- gravity
- the swimmer pushing on the wall
- the water's friction
the wall pushing back on the swimmer
Hint: The swimmer pushes the wall (action), and the wall pushes the swimmer (reaction). Only the force on the swimmer moves the swimmer.