Question

introducing physical science for grades 4 - 6
name:
date:
chapter xi: understanding inertia (cont.)
friction and heat
friction produces heat. this is why rubbing your hands together in the winter warms them up. the friction is producing heat. the rougher the surfaces of the objects, the more heat is produced. two rough objects rubbed together produce more heat than two smooth objects rubbed together.
select the choice in each pair that would have the greater friction. this choice would also produce more heat.

1. a) walking on ice b) walking on the sidewalk
2. a) turning a bicycle chain without oil b) turning a bicycle chain with oil
3. a) rubbing greasy hands together b) rubbing dry hands together
4. a) riding a bicycle in gravel b) riding a bicycle on the highway
5. a) rubbing two pieces of sandpaper together b) rubbing two pieces of notebook paper together
6. a) rolling a bowling ball through grass b) rolling a bowling ball down a bowling lane
7. a) playing volleyball in the gym b) playing volleyball on the sand at the beach
8. a) stopping a bicycle with the brake b) letting a bicycle roll to a stop
9. a) stirring a bowl of sand b) stirring a bowl of milk
10. a) pushing a brick b) pushing a book
11. the choices with greater friction would produce ( more / less ) heat.

Explanation:

1. Walking on the sidewalk (b) has greater friction than walking on ice (a) because ice is smoother.
2. Turning a bicycle chain without oil (a) has greater friction than with oil (b) as oil reduces friction.
3. Rubbing dry hands together (b) has greater friction than greasy hands (a) since grease makes hands smoother.
4. Riding a bicycle in gravel (a) has greater friction than on the highway (b) as gravel is rougher.
5. Rubbing two pieces of sandpaper together (a) has greater friction than notebook paper (b) because sandpaper is rougher.
6. Rolling a bowling ball through grass (a) has greater friction than down a bowling lane (b) as grass is rougher.
7. Playing volleyball on the sand at the beach (b) has greater friction than in the gym (a) as sand is rougher.
8. Stopping a bicycle with the brake (a) has greater friction than letting it roll to a stop (b) as the brake creates more resistance.
9. Stirring a bowl of sand (a) has greater friction than milk (b) as sand particles are rough.
10. Pushing a brick (a) has greater friction than a book (b) as a brick has a rougher surface.
11. The choices with greater friction would produce more heat as per the text "Friction produces heat. The rougher the surfaces of the objects, the more heat is produced".

Answer:

1. b
2. a
3. b
4. a
5. a
6. a
7. b
8. a
9. a
10. a
11. more