Year 7 Revision 1. What is a force? ________________________________________________________________________ _______________________________________________________________________ 2. A push is a force of ________________ (PULRESION) where objects get _________ (THUFURRE) apart and a pull is a force of _________________ (ATRTCINOAT) where objects get ____________ (SLOCER) together. 3. Explain the difference between a contact and a non-contact force: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 4. list two examples of contact forces and two examples of non-contact forces: Contact forces: Non-contact forces: 5. For each of the images below, decide whether the forces on the object are balanced or unbalanced and state the direction it will move. 5N 25 N 20 N 5N 12 N 10 N 5N Balanced or unbalanced Direction - Balanced or unbalanced Direction - Balanced or unbalanced Direction - 6. Explain what a friction force is. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 7. State one example of a situation where friction is helpful and explain what would happen if there was no friction involved. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 8. Explain why your shoes get holes in them if you wear them for a long time. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 9. Explain why your hands get warmer when you rub them together. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 10.What is an example of a situation where you would want friction to produce heat? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 11.What is an example of a situation where you would want friction to produce wear? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 12. Steve the caveman is trying to move his fridge to the other side of his cave. The issue is that there is far too much friction between the fridge and the ground and Steve can’t move it. At the moment the fridge is full of heavy dinosaur steaks and the cave kitchen floor is covered in rough gravel. a) State two ways that Steve could reduce the amount of friction and then explain why each of these methods would work. Method of reducing friction: __________________________________________________ Why this reduces friction: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ Method of reducing friction: __________________________________________________ Why this reduces friction: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ b) State two other ways that friction can be reduced: ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 13.Define the following terms: Newton- ________________________________________________________________ ________________________________________________________________________ Magnetic field -___________________________________________________________ ________________________________________________________________________ Classify the following materials as either magnetic or non-magnetic: Iron Copper Wood Aluminium Magnetic Steel Nickel Non-magnetic 14. Explain why a compass needle will align to point North. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 15.Explain why a common bar magnet will not align to point North like that in a compass. ___________________________________________________________________________ ___________________________________________________________________________ 16.How could you make a bar magnet point North like a compass? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 17.Explain how a compass would be affected if a bar magnet was held nearby. Would the compass still work? ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ 18. Indicate whether the magnets below will attract or repel each other. A) N S S N __________________________________________________ B) N S N S _________________________________________________________________ 19. Count the number of magnetic field lines in each of the circles on the right. 1 - ________________ 1 2- ________________ 2 20. Using the information in the previous question, explain why the magnet gets weaker as they move further away. ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________ ___________________________________________________________________________