The acceleration of a particle along a straight line is defined by a=(2t−9)m/s2a=(2t−9)m/s2, where tt is in seconds. At tt = 0, ss = 1 mm and vv = 10 m/sm/s.

It's a snowy day and you're pulling a friend along a level road on a sled. you've both been taking physics, so she asks what you think the coefficient of friction between the sled and the snow is. you've been walking at a steady 1.5m/s, and the rope pulls up on the sled at a 32 ∘ angle. you estimate that the mass of the sled, with your friend on it, is 65 kg and that you're pulling with a force of 80 n .