ap physics 1 momentum collision question

Question

The store calls the mall security and the former sales clerk takes off running. She decides to hide out with her friend who runs the kiddy choo-choo. She is driving the 510. kg train (including all passengers) at a constant 0.667 m/s when it comes off the tracks and coasts (at that speed) into a large present that was part of the holiday display. The present and the train stick together during the collision. If the coefficient of friction between the 20.0 kg present and the floor is 0.50, find the distance the train travels before coming to rest. (Hint, only the present’s normal force causes the force of friction.)

Answer 1

Hi Tapti C.,m

So the present is exerting a frictional force of µmg = 0.5*9.8 m s^-2 * 20 kg. The combined momentum is what the train etc. brought in initially = 510 kg *0.667 m s^-1 . The present mass (combined) you can figure out, and therefore the initial velocity of train+present. What is the equation for acceleration, mass, and force? You get acceleration from that. And what is the equation for initial velocity, final velocity, acceleration, and distance travelled? You get the distance travelled from that.

-- Cheers, --Mr. d.