# Velocity on a hill Kinematics Problem with Dynamics

In the sport of luge, a competitor slides on a sled down a 500-m long straight ice track inclined at 20o to the horizontal. Her initial speed is 2.0 m s-1. The coefficient of dynamic friction between the sled and the ice is 0.050. Neglect air resistance.

What is her acceleration? What is her speed at the bottom?

Okay, this is weird.

I spent three hours on this. I feel the mass of the competitor is missing.

I separated the two dimensions. Both have non-zero acceleration (because there is a net force that is diagonal to the ice).

I get these equations:

-171=-0.68+1/2(-1.15+0.017/m)t^2

469=1.88t+1/2(3.15-0.047/m)t^2

a=3.35-0.05/m

I can’t solve because I get 0=0 on both sides if I try to add the equations.

What am I supposed to do? Please, I have an exam soon.

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