21. A 3.00-kg crate slides down a ramp that is 1.00 m in length and inclined at an angle of 30.0 as shown in the figure. The crate starts from rest at the top and experiences a constant friction force of magnitude 5.00 N. As the crate reaches the bottom of the ramp, it collides with a second, identical crate. If both crates stick together after the collision and experience a combined frictional force of 10.0 N, how far do they slide? a) Use an energy conservation approach to determine the speed of the first crate at the end of the ramp (just before it hits the second crate). (5 points) b) Write down an expression of momentum conservation that describes the system of the two crates just before and just after the collision. (5 points) c) Use a momentum conservation approach to = 0 d = 1.00 m 0.500 m 30.0 determine the initial speed with which the two crates are sliding across the horizontal floor. Assume the collision occurs just after the first crate has left the ramp. (5 points) d) Determine the distance the two crates are sliding together (Hint: there are multiple ways you can do this, but thinking about energy conservation may save you a lot of work here). (5 points)