7. A 3.00-kg crate slides down a ramp. The ramp 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. The crate continues to move a short distance on the horizontal floor after it leaves the ramp, and then comes (a) Use energy methods to determine the speed of the crate at the bottom of the ramp. (b) How far does the crate slide on the horizontal floor if it continues to experience a friction force of magnitude 5.00 N?8. A block having a mass of 0.80 kg is given an initial velocity VA = 1.2 m/s to the right and collides with a spring whose mass is negligible and whose force constant is k = 50 N/m as shown in the figure. (a) Assuming the surface to be frictionless, calculate the maximum compression of the spring after the collision. (b) Suppose a constant force of kinetic friction acts between the block and the surface, with / = 0.50. If the speed of the block at the moment it collides with the spring is ya = 1.2 m/s, what is the maximum compression to in the spring? 9. An elevator car has a mass of 1,600 kg and is carrying passengers having a combined mass MOlor of 200 kg. A constant friction force of 4,000 N retards its motion. (a) How much power must a motor deliver to lift the elevator car and its passengers at a constant speed of 3.00 m/'s? (b) What power must the motor deliver at the instant the speed of the elevator is v if the motor is designed to provide the elevator car with an upward acceleration of 1.00 m/'s