Forces
Science, Physics. Usually met in years 8 to 11.
Use weight, force and acceleration, and find the resultant of forces acting in opposite directions.
What you practise
- Weight = mass × gravitational field strength
- Force = mass × acceleration
- Resultant force
Ends with a car’s acceleration from driving force and resistance. Practice moves up a level when a round goes well and down when it does not.
Sample questions
Each sample comes with the method and the reason every wrong option is wrong. Real practice rounds are ten questions at your level.
Sample question, level 2 of 5
A force acts on a 31 kg object and gives it an acceleration of 3 m/s². What is the force?
- 930 N
- 0.097 N
- 10.333 N
- 93 N
- 34 N
Show the answer and method
Answer: D, 93 N
The method: Force = mass × acceleration = 31 × 3 = 93 N.
Why the other options are wrong:
- A, 930 N: The decimal point is one place out.
- B, 0.097 N: The division is upside down. Force = mass × acceleration.
- C, 10.333 N: The mass was divided by the acceleration. Force = mass × acceleration.
- E, 34 N: The mass and acceleration were added.
Sample question, level 4 of 5
A box is pushed to the right with a force of 90 N. Friction pushes to the left with a force of 40 N. What is the resultant force?
- 50 N to the right
- 90 N to the right
- 40 N to the left
- 50 N to the left
- 130 N to the right
Show the answer and method
Answer: A, 50 N to the right
The method: The forces act in opposite directions, so subtract: 90 − 40 = 50 N, in the direction of the larger force, to the right.
Why the other options are wrong:
- B, 90 N to the right: The friction force was ignored.
- C, 40 N to the left: This is only the friction force.
- D, 50 N to the left: The size is right but the direction is wrong: the larger force is to the right.
- E, 130 N to the right: The forces were added, but they act in opposite directions, so they partly cancel.
See where this fits: GCSE science with AQA and Key Stage 3.
Related topics: Density, Electricity, Energy, Waves.
