BR physics chapter 3 passage 2 number 14

[2010premed]

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compare the linear speeds at point 3 for one child, who just slides down the slide, to that for another, who rolls down the slide
A. v slider< v roller
B. v slider > v roller
C. v slider = v roller
D. More info is needed to answer the question

Why isn't it A, as the slider would experience more friction?
Also why isn't it D, as we need to know the initial velocity?

 

[The Dr T]

compare the linear speeds at point 3 for one child, who just slides down the slide, to that for another, who rolls down the slide
A. v slider< v roller
B. v slider > v roller
C. v slider = v roller
D. More info is needed to answer the question

Why isn't it A, as the slider would experience more friction?
Also why isn't it D, as we need to know the initial velocity?

I believe for that question, the slide at that point was frictionless.

You have to remember that during rolling, some of the Energy from linear motion gets transferred to rolling KE. This depends on the shape of the object; generally its 1/2*I*w^2, where I is the moment of inertia.

Therefore, instead of all the PE being converted to linear KE (1/2 m*v^2), some of it is being transferred to 1/2*I*w^2, and thus the slider must be faster than the roller at the end of the FRICTIONLESS slide.

Hope that helps.

 

[2010premed]

you're right, it was frictionless. Thanks so much!