Power
What is the units for Power
Watts
What are the Units of Work
Joules
What does the total energy equal?
E = PE + KE + Q
What is the equation for the potential energy in a spring?
(1/2)kx2
What is the units for Energy?
Joules
What is the definition of Power?
The rate at which work is done
A student does 60 joules of work pushing a box up a ramp that is 5.0 meters long. What is the magnitude of the force applied to the box to do this work?
12N
What is important to know about the energy in a system?
The total energy is constant.
Energy is conserved
A spring with a spring constant of 80 newtons per meter is displaced 0.30 meter from its equilibrium position. The potential energy stored in the spring is
3.6J
A 45-kilogram boy is riding a 15-kilogram bicycle with a speed of 8 meters per second. What is the combined kinetic energy of the boy and the bicycle?
1920J
A boat weighing 900 newtons requires a horizontal force of 600 newtons to move it across the water at 15 meters per second. The boat’s engine must provide work at the rate of
9,000W
How much work is done if a 900 Newton bodybuilder lifts a 20 Newton box 2 meters?
40J
What is the gravitational potential energy with respect to the surface of the water of a 75.0-kilogram diver located 3.00 meters above the water?
2,205J
The spring in a scale in the produce department of a supermarket stretches 0.025 meter when a watermelon weighing 100 newtons is placed on the scale. The spring constant for this spring is
4,000 N/m
Draw a KE v h graph for an object thrown upwards.
Indirect starting at (0,#)
A motor used 120 watts of power to raise a 15-newton object in 5.0 seconds. Through what vertical distance was the object raised?
40m
What is the relationship between work and kinetic energy?
The net work is equal to the change in kinetic energy
A 0.50-kilogram ball is thrown vertically upward with an initial kinetic energy of 25 joules. Approximately how high will the ball rise?
5.1m
A 5-newton force causes a spring to stretch 0.2 meter. What is the potential energy stored in the stretched spring?
0.5J
If a car is skidding on its brakes, what is the kinetic energy being converted to?
Internal Energy
A 40-kilogram student runs up a staircase to a floor that is 5.0 meters higher than her starting point in 7.0 seconds. The student’s power output is
280W
A 15.0-kilogram mass is moving at 7.50 meters per second on a horizontal, frictionless surface. What is the total work that must be done on the mass to increase its speed to 11.5 meters per second?
570J
A 3.00-kilogram ball is dropped from the top of a building. Just before striking the ground, the ball’s speed is 12.0 meters per second. What was the ball’s gravitational potential energy, relative to the ground, at the instant it was dropped?
216J
A compressed spring in a toy is used to launch a 5.00-gram ball. If the ball leaves the toy with an initial horizontal speed of 5.00 meters per second, the minimum amount of potential energy stored in the compressed spring was
0.0625J
A 40-Newton box is pushed up a 2-meter high ramp. What is the gravitational potential energy at the top of the ramp?
80J