TBR Content Example

[ilovemcat]

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What would you say the answer to this question is. (If you have TBR, don't cheat 🙂)

A Child riding on a merry-go-round jumps off a horse and starts walking toward the center of the ride. As he moves, the acceleration he feels:

A. increases, because his tangential speed decreases
B. increases, because his radius from the center decreases.
C. decreases, because his tangential speed increases.
D. decreases, because his radius from the center decreases.

 

[PiBond]

What would you say the answer to this question is. (If you have TBR, don't cheat 🙂)

A Child riding on a merry-go-round jumps off a horse and starts walking toward the center of the ride. As he moves, the acceleration he feels:

A. increases, because his tangential speed decreases
B. increases, because his radius from the center decreases.
C. decreases, because his tangential speed increases.
D. decreases, because his radius from the center decreases.

My guess is D.

 

[TwoPaddles]

What would you say the answer to this question is. (If you have TBR, don't cheat 🙂)

A Child riding on a merry-go-round jumps off a horse and starts walking toward the center of the ride. As he moves, the acceleration he feels:

A. increases, because his tangential speed decreases
B. increases, because his radius from the center decreases.
C. decreases, because his tangential speed increases.
D. decreases, because his radius from the center decreases.

lol I just remembered they used the formula a = omega^2 * r
So if r is decreasing, so does the acceleration.

 

[ilovemcat]

My guess is D.

Yep, you're right! It's a tricky question. Because velocity decreases and radius decreases, they used an alternative equation to find out how acceleration would be affected (a = angular velocity² x radius). Knowing me, I probably would of been like WTF and guessed lol.

 

[ilovemcat]

lol I just remembered they used the formula a = omega^2 * r
So if r is decreasing, so does the acceleration.

Yep, haha. 👍

 

[PiBond]

To me, this is one of those intuition type question. I think of physical scenarios (ie swinging on a marry-go-round) that I've experienced and narrow it down to C and D. When I was a kid and my arms got tired from hanging onto the unicorn, I'd walk inward to the middle to take a break.

My tangential speed wouldn't be increasing in the sense that I'm not covering more distance with time. Therefore, D is the only option.

 

[Rabolisk]

There are a couple ways of looking at this problem. First, note that you have a uniform circular motion (even though the velocity and acceleration change as the child goes towards the center, the motion itself is uniform circular). The formula is centripetal acceleration = v^2/r = ɷ^2*r, where v is tangential speed and ɷ is angular speed. What you have to realize is that v is not constant, whereas ɷ is.

 

[TwoPaddles]

There are a couple ways of looking at this problem. First, note that you have a uniform circular motion (even though the velocity and acceleration change as the child goes towards the center, the motion itself is uniform circular). The formula is centripetal acceleration = v^2/r = ɷ^2*r, where v is tangential speed and ɷ is angular speed. What you have to realize is that v is not constant, whereas ɷ is.

Word.