An 0.80-kg block is held in place against the spring by a 67-N ...

[Collmarie]

An 0.80-kg block is held in place against the spring by a 67-N horizontal external force (see the figure). The external force is removed, and the block is projected with a velocity v1 = 1.2 m/s upon separation from the spring.
 
  The block descends a ramp and has a velocity v2 = 1.9 m/s at the bottom. The track is frictionless between points A and B. The block enters a rough section at B, extending to E. The coefficient of kinetic friction over this section is 0.39. The velocity of the block is v3 = 1.4 m/s at C. The block moves on to D, where it stops. The spring constant of the spring is closest to
 
  A) 3900 N/m.
  B) 2600 N/m.
  C) 2000 N/m.
  D) 1600 N/m.
  E) 1100 N/m.

Question 2

A 50.0-kg skier starting from rest travels 200 m down a hill that has a 20.0 slope and a uniform surface. When the skier reaches the bottom of the hill, her speed is 30.0 m/s.
 
  (a) How much work is done by friction as the skier comes down the hill?
  (b) What is the magnitude of the friction force if the skier travels directly down the hill?
  What will be an ideal response?

[ricroger]

Answer to Question 1

Answer: A

Answer to Question 2

Answer: (a) -1.10  104 J (b) 55.3 N

[Collmarie]

Wow, this really help

[milbourne11]

Excellent