Ravi rolls the same ball with the same push on three floors…
Contributed by StemPy LabTry it on paper first. A hint, the key idea and the worked solution are here when you need them.
Ravi rolls the same ball with the same push on three floors. It stops after on carpet, on wood and on ice.
- Why does it stop at all?
- Where is friction biggest?
- Ravi says: 'With no friction it would never stop.' Is he right?
- Does a moving ball need a force to keep it moving?
Need a reminder? The key ideaShow
Newton's first law: an object stays at rest, or keeps moving in a straight line at a steady speed, unless an unbalanced force acts on it. Inertia is this tendency to keep the same motion; more mass means more inertia.
Friction acts between surfaces that touch, against sliding. It matches a push up to a limit; once the object slides, friction is usually a little less than that limit.
The worked solution
Have you tried it?
Work it out on paper first. It is fine to get stuck or make a mistake: that is how we learn. When you are ready, go through the solution one step at a time, and check each step against your own.
Step 1. (a) Friction (and a little air) is an unbalanced force against its motion.
Step 2. (b) On carpet: it stops in the shortest distance, so it is slowed the most.
Step 3. (c) Yes. By the first law, with no unbalanced force it would roll on in a straight line at a steady speed.
Step 4. (d) No. A force is needed to change the motion, not to keep it.
Answer: Friction stops it; carpet; Ravi is right; no. On ice it rolls times as far as on carpet.
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