Contact and non-contact forces — AQA GCSE Physics
Test yourself on Contact and non-contact forces with AQA GCSE practice questions.
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Contact and non-contact forces explained
Contact forces need the two objects to be touching.
Read the full explanation
Friction acts along the surfaces where two objects slide or try to slide past each other, always opposing the relative motion. Air resistance, and water resistance, are the friction of a fluid on an object moving through it, and grow larger as the object speeds up. Tension is the pull along a stretched rope, cable or spring, pulling inwards on whatever is attached at each end. The normal contact force is the push of a surface on an object resting against it, acting at right angles to that surface. Upthrust, the upward push of a fluid on an immersed object, is also a contact force and is accepted in answers.
Your focus
- Name three contact forces other than friction and air resistance.
- Identify all the contact forces acting on an object resting on the bottom of a pool.
- Describe the direction in which the normal contact force and friction each act on a sliding object.
Contact and non-contact forces exam tips
Marking Points
- one mark for a named contact force other than those already given in the question, such as tension, normal contact force or upthrust
- one mark for the two objects being physically in contact while the force acts
- one mark for using the full name, normal contact force or normal reaction force, rather than 'reaction' alone
- one mark for identifying every contact force acting in a described situation, such as upthrust and normal contact force on a brick lying on the bottom of a pool
Examiner Tips
- 💡Check which forces the question has already named, because repeating one of them scores nothing.
- 💡Lift, thrust and water resistance are all accepted, so you have more than three safe answers available.
- 💡Say 'normal contact force' in full; it takes two extra words and secures the mark.
Common Mistakes
- answering 'drag', which examiners ignore because it repeats air resistance already given
- offering gravity or weight, which are non-contact forces
- writing 'reaction' on its own instead of normal contact force
- describing friction as a force that acts in the direction of motion
- leaving upthrust out when listing the forces on a submerged object