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pgardn

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## Homework Statement

I am a substitute today for a physics class. I am baffled by the following and could use some help.

A 0.50 kg ball sits on a cart. When the cart is pulled to the right by a net force of 3N, friction exerts a force of 2.0 N on the bottom of the ball. The ball rolls without slipping, how far will the ball roll relative to the ground in 0.10S.

## Homework Equations

: [/B]I took this to be a 2nd law problem with kinematics as the mass of the cart is not given. And there is nothing about I or the radius of the ball on top of the cart.

F=ma delta x = vot + 1/2at^2

## The Attempt at a Solution

I decided there was one force in the horizontal acting on the ball to the left, so F=ma.

2N = 0.5 kg (a) I assumed this 2N force was to the left a = 4 m/s/s

Now delta x = 0 + 1/2at^2 delta x = 1/2(4)(0.1)^2 delta x = 0.02 m as an answer

But then I started to think relative to the ground. And since the ball is rolling on a cart that is accelerating right, I needed to determine how far the cart would move. But I had no info on the mass of the cart. So I thought the ball really just had one force acting on it and would begin to move on the cart like it was frictionless and act like some sort of wind was applying a force of 2N to the left. Then I stopped in complete bafflement.

[Mentor's note: Removed bold formatting from text content]

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