A motorist traveling with a constant 15m/s passes a school crossing conner where the speed limit is 10m/s, just as a motorist passes RTSA officer of a motor cycle stoped at a conner, start off in pursuit with constant acceleration of 3m/s^2. (a) how much time elapses before the officer catches up the motorist?
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Modify the equation fδt=δ (mv) to find the force of friction.

A23 kg log of wood begins from rest, 300 m up a sluice (a water track used to transport logs, think of it as an inclined plane with negligible friction) inclined at 20° to the horizontal. after it reaches the flat waterway at the bottom it collides elastically with a 100 kg block of wood initially at rest near the base of the incline. (a) how long does it take the 23 kg log to travel down the incline? (b) what is the speed of the 23 kg log at the bottom of the incline? (c) what are the velocities of both blocks of wood after the collision? (d) what is the total kinetic energy before the collision? (e) what is the kinetic energy of the 23 kg log after the collision? (f) what is the kinetic energy of the 100 kg block of wood after the collision? (g) what is the total kinetic energy after the collision? (h) compare the total initial and total final kinetic energies. is this consistent with what you would expect for elastic collisions? explain!

What is the measure of a change in an objects velocity?