NotTim 3 years ago Simple practical application (no math): A child is standing on a slowly rotating ride in a park. the ride operator makes the statement that in Earth's frame of reference, the child remains at the same distance from the centre of the ride because there is no net force acting on him. Do you agree with this statement? Explain your answer.

1. NotTim

MY ANSWER: Yes, I agree with this statement because the child maintains a constant radius throughout the ride. @ every point on the ride, there is the same gravitational force and centripetal force throughout

2. NotTim

I'm sorry but that is NOT a viable option.

3. NotTim

uhh

4. YesterdayiSaidTomorow

da fuk is Earth's frame of reference?

5. NotTim

txtbook.

6. NotTim
7. YesterdayiSaidTomorow

8. YesterdayiSaidTomorow

this site sux

9. NotTim

lol like i trust yahoo answers.

10. YesterdayiSaidTomorow

hey mang, it's better than nothing

11. NotTim

NOThing

12. NotTim

I'm going to sleep. If anyone responds. I'll be back.

13. eseidl

I disagree. In the Earth's frame the child is moving in a circle. Since his velocity vector is constantly changing, his acceleration is NOT zero, thus there must be a net force acting on him.

14. eseidl

The net force acting on him is the centripetal force. It is the force that causes him to move in a circle. If there were no net force acting on him, he would continue to move in a straight line at content speed.

15. eseidl

constant*

16. NotTim

But relative to the earth's frame of reference?

17. eseidl

My answer is relative to the Earth's frame.

18. NotTim

so, really, the only reason why the child remains the same distance from the centre of the ride is because of the constant radiu, and not the force?

19. eseidl

Your answer states that you agree because there is the same net gravitational and centripetal force throughout the motion. It is true that the net forces are constant throughout the motion. The ride operator argues that there is NO net force on the kid. Obviously this is not correct, the kid isn't moving in a straight line at constant speed (Newton's first law).

20. NotTim

so, the correct answer is that although the child remains the same distance from the centre, their still is a net force acting upon him?

21. eseidl

the centripetal force is what keeps the kid at a constant distance from the center of the circle. If the centripetal force changed, the radius would change. In the extreme case, where the centripital force vanishes, the kid would fly off in straight line, away from the centre of the circle. |dw:1349029423494:dw|

22. eseidl

That's absolutely correct

23. NotTim

thx then

24. eseidl

Technically the centripetal force isn't constant. It has a constant magnitude, but the direction of the force is always changing (it is always pointing to the center of the circle as the kid moves around). The direction of the force is changing so it isn't a "constant" force.

25. eseidl

no problem. I hope this makes sense. Basically, the only time there is no NET force on an object is when the object moves in a straight line at constant speed. If either the speed or the direction of motion are not constant, there MUST be a NET force.