Download work energy and power extra practice

1. Apply the work equation to determine the amount of work done by the applied force in each of
the three situations described below.
2. The following descriptions and their accompanying free-body diagrams show the forces acting
upon an object. For each case, indicate which force(s) are doing work upon the object. Then
calculate the work done by these forces.
A 10-N force is applied to push a block across a friction free surface for a displacement of 5.0 m
to the right.
A 10-N frictional force slows a moving block to a stop after a displacement of 5.0 m to the right.
A 10-N force is applied to push a block across a frictional surface at constant speed for a
displacement of 5.0 m to the right.
An approximately 2-kg object is sliding at constant speed across a friction free surface for a
displacement of 5 m to the right.
An approximately 2-kg object is pulled upward at constant speed by a 20-N force for a vertical
displacement of 5 m.
3. Ben carries a 200-N suitcase up three flights of stairs (a height of 10.0 m) and then pushes it
with a horizontal force of 50.0 N at a constant speed of 0.5 m/s for a horizontal distance of 35.0
meters. How much work does Ben do on his suitcase during this entire motion?
4. How much work is done by an applied force to lift a 15-Newton block 3.0 meters vertically at
a constant speed?
5. A student with a mass of 80.0 kg runs up three flights of stairs in 12.0 sec. The student has
gone a vertical distance of 8.0 m. Determine the amount of work done by the student to elevate
his body to this height. Assume that his speed is constant.
6. A cart is loaded with a brick and pulled at constant speed along an inclined plane to the height
of a seat-top. If the mass of the loaded cart is 3.0 kg and the height of the seat top is 0.45 meters,
then what is the potential energy of the loaded cart at the height of the seat-top?
7. If a force of 14.7 N is used to drag the loaded cart (from previous question) along the incline
for a distance of 0.90 meters, then how much work is done on the loaded cart?
8. Determine the kinetic energy of a 625-kg roller coaster car that is moving with a speed of 18.3
m/s.
9. If the roller coaster car in the above problem were moving with twice the speed, then what
would be its new kinetic energy?
10. Missy, a platform diver for the Ringling Brother's Circus, had a kinetic energy of 12, 000 J
just prior to hitting the bucket of water. If Missy's mass is 40 kg, then what is her speed?
11. A 900-kg compact car moving at 60 mi/hr has approximately 320, 000 Joules of kinetic
energy. Estimate its new kinetic energy if it is moving at 30 mi/hr. (HINT: use the kinetic energy
equation as a guide no hard calculation is necessary)