Primary 6 · Science · Interactions: Forces
Interactions: Forces questions for Primary 6 Science
10 questions to work through online, 2 of them written out the way the paper asks. Answer and you get the working straight away, then a score at the end. No sign-up, and you can retake it as often as you like.
- Balanced forces
- Unbalanced forces
- Mass and weight
- Elastic force
- Friction in air and water
- Identifying forces at work
- Reasoning about a change
- Naming the unit
- Naming a force
- Applying the ideas
| Trolley | Forward force (N) | Backward force (N) |
|---|---|---|
| P | 12 | 12 |
| Q | 20 | 8 |
| R | 6 | 15 |
| Load on the spring (N) | Length of spring (cm) |
|---|---|
| 0 | 10 |
| 2 | 13 |
| 4 | 16 |
| 6 | 19 |
Answers and explanations for all 10 questions
Every answer with the reasoning behind it. Worth reading after you have tried the set — or on its own, if you are a parent marking it.
A lorry travels along a straight road at a steady speed. What can be said about the forces on it?
Answer: They are balanced.
Steady speed in a straight line means the forces cancel out. They are balanced, which is not at all the same as being absent.
Based on the table above, which trolley speeds up?
Answer: Q
Q has 20 N forward against 8 N back, so there is a net force of 12 N forward. An unbalanced force in the direction of travel makes it speed up.
Which two statements about mass and weight are correct?
Answer: A and B only
Mass is how much matter there is, measured in grams, and it travels with the object. Weight is the pull of gravity on it, measured in newtons, and it changes with where you are.
Based on the table above, what would the spring's length be with a load of 8 N?
Answer: 22 cm
Each extra 2 N stretches the spring by 3 cm: 10, 13, 16, 19. Another 2 N takes it to 22 cm.
In the set-ups above, the ball in B took much longer to reach the bottom. Why?
Answer: Water resists the ball's movement much more than air does.
Both balls are pulled down by the same weight. Water is far denser than air, so it opposes the movement much more strongly and the ball falls slowly.
A parachutist falls at a steady speed. Which two forces are acting?
Answer: A and B only
Weight pulls the parachutist down and air resistance pushes up. At steady speed the two are equal, which is why the fall neither speeds up nor slows.
A cyclist stops pedalling on a flat road and gradually slows to a stop. Which explanation is correct?
Answer: Friction and air resistance act backwards with nothing driving forwards.
Once pedalling stops there is no forward force, but friction in the wheels and air resistance keep acting backwards. That unbalanced force slows the bicycle.
Force is measured in a unit named after a famous scientist. What is that unit called?
Answer: newton
Force is measured in newtons.
A stretched spring pulls back towards its original length. What kind of force is this? ______ force.
Answer: elastic
The pull of a stretched spring returning to shape is elastic force.
A 500 g bag of rice is weighed on Earth and again on the Moon, where gravity is about one sixth as strong. Which pair of readings is correct?
Answer: 500 g on both, but a smaller reading in newtons on the Moon
The rice still contains 500 g of matter wherever it is. What changes is the pull on it, so a spring balance reading in newtons falls to about a sixth.