Suppose an object slides up a ramp, slowly comes to a stop, then slides back down. The net force (which is the sum of all the forces acting on the object) is:

Two crates of fruit  are released from the top of a ramp inclined at 30 degrees from the horizontal and 4.5 meter long. The two crates consist of  an apple crate of mass 20 kg that is placed in front of a watermelon crate of mass 80 kg.  The apple crate has a coefficient of friction of 0.20 while the watermelon crate has a coefficient of friction of 0.15. How long does it take the apple crate to reach the bottom of the incline if it needs to travel a distance of 4.5 meters?

The standing vertical jump is a good test of an athlete’s strength and fitness. The athlete goes into a deep crouch, then extends his legs rapidly; when his legs are fully extended, he leaves the ground and rises to his highest height. It is the force of the ground on the athlete during the extension phase that accelerates the athlete to the final speed with which he leaves the ground. A good jumper can exert a force on the ground equal to twice his weight. If his crouch is 60 cm deep, how far off the ground does he rise?

Two buckets of sand hang from opposite ends of a rope that passes over an ideal pulley. Onebucket is full and weighs 120 N; the other bucket is only partlyfilled and weighs 63 N. (a) Initially, you hold onto the lighterbucket to keep it from moving. What is the tension in the rope?(b) You release the lighter bucket and the heavier one descends.What is the tension in the rope now? (c) Eventually the heavierbucket lands and the two buckets come to rest. What is the tension in the rope now? Show your work and explain