A puck of mass 0.03 kg slides across rough ice, experiencing a frictional force of 0.2 N. If it was moving at 36 m/s when I hit the ice patch,

A) How long did it take to stop?
B) What was the length of the ice patch?

I know I have initial velocity, mass and final velocity of 0. How do I find time? Is it considered uniform motion?

1 answer

Since F=ma, the 0.2N friction causes a deceleration of .2/.03 = 1.67 m/s^2

so, its speed and position are described by

v = 36 - 1.67t
s = 36t - 0.83 t^2

You can find t when v=0 (stopped) and use that value to find the stopping position.

Not uniform motion, but uniform acceleration.