P4 Science · Chapter 14brightbit.net/worksheets
Forces — Friction
Name: ______________________Class: ________Date: ____________Score: ____ / 10
- 1.
What is frictional force?
(a) The force that pulls objects towards the Earth(b) A force that opposes the relative motion between two surfaces in contact(c) The force stored in a stretched spring(d) The force that makes objects float in water
- 2.
Which surface would produce the MOST friction?
(a) Ice(b) Glass(c) Sandpaper(d) Polished marble
- 3.
Why are the soles of shoes designed with grooves and patterns?
(a) To make the shoes look more attractive(b) To increase friction between the shoe and the ground to prevent slipping(c) To reduce the weight of the shoes(d) To allow water to drain away from inside the shoe
- 4.
A car's brakes work by pressing brake pads against the wheel disc. How do the brakes slow the car?
(a) The brake pads add force to speed up the wheel in the opposite direction(b) Friction between the brake pads and disc converts kinetic energy to heat, slowing the wheel(c) The brake pads absorb the electricity powering the car(d) The brakes increase gravity acting on the car
- 5.
Which of the following is an example where friction is HELPFUL?
(a) Friction between a bicycle chain and gears causing wear(b) Friction between car tyres and the road allowing the car to steer and brake(c) Friction between machine parts reducing efficiency(d) Friction making it harder to slide furniture across a floor
- 6.
Which of the following is an example where friction is UNHELPFUL?
(a) Friction helping you grip a pen while writing(b) Friction allowing you to walk without slipping(c) Friction in engine parts causing heat and energy loss(d) Friction of matches against a rough surface producing fire
- 7.
How does oil reduce friction between engine parts?
(a) Oil absorbs heat from the engine(b) Oil creates a thin film between surfaces, preventing direct contact and reducing friction(c) Oil makes the metal parts harder(d) Oil conducts heat away from the moving parts
- 8.
A student pushes a box across the floor. The box is harder to move on a rough concrete floor than on a smooth tiles floor. Why?
(a) The concrete floor is harder, so it pushes back with more force(b) The rough concrete surface has more microscopic bumps that interlock with the box, increasing friction(c) The concrete floor is heavier, so it resists movement more(d) The tiles floor has more gravity acting on it
- 9.
Give ONE example where increasing friction is useful and ONE example where decreasing friction is useful.
- 10.
A skydiver jumps from a plane. At first she accelerates downwards. After some time, she reaches a constant speed called terminal velocity. Explain why she stops accelerating.
Answer key — P4 Science: Forces — Friction
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- 1.(b) A force that opposes the relative motion between two surfaces in contact
- 2.(c) Sandpaper
- 3.(b) To increase friction between the shoe and the ground to prevent slipping
- 4.(b) Friction between the brake pads and disc converts kinetic energy to heat, slowing the wheel
- 5.(b) Friction between car tyres and the road allowing the car to steer and brake
- 6.(c) Friction in engine parts causing heat and energy loss
- 7.(b) Oil creates a thin film between surfaces, preventing direct contact and reducing friction
- 8.(b) The rough concrete surface has more microscopic bumps that interlock with the box, increasing friction
- 9.increasing: shoe soles on wet floors; decreasing: oiling bicycle chains to reduce wear
- 10.as she speeds up, air resistance increases until it equals gravitational force, so the net force becomes zero and she falls at a constant speed
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