Definitions
stored energy
What is Potential Energy?
A garden tractor drags a plow with a force of 500 Newtons a distance of 5 meters in 10 seconds. How much work is done?
a)50 joules
b)2500 joules
c)5000 joules
d) 100 joules
What is choice b) 2500 Joules?
Energy
Joules
A spring has a spring constant of 120 newtons per meter. How much potential energy is stored in the spring as it is stretched 0.20 meter?
2.4 J
the rate at which work is done
What is Power?
How long would it take a machine to do 5000 Joules of work if the power rating of the machine is 100 watts?
a)0.2 seconds
b)10 seconds
c)50 seconds
d)5000 seconds
What is c) 50 seconds?
Work
Joules
Spring A has a spring constant of 140 newtons per meter, and spring B has a spring constant of 280 newtons per meter. Both springs are stretched the same distance. Compared to the PE stored in spring A, the potential energy stored in spring B is
a)the same
b) twice as great
c)half as great
d) four times as great
b) twice as great
Energy of motion
What is kinetic energy?
Which action would require no work to be done on an object?
a)lifting the object from the floor to the ceiling
b)pushing the object along a horizontal floor against a frictional force
c)decreasing the speed of the object until it comes to rest
d) holding the object stationary above the ground
What is d) holding the object stationary above the ground?
Power
Watts
A 20 kg object strikes the ground with 1960 J of kinetic energy after falling freely from rest. How far above the ground was the object when it was released?
10 meters
The ability of a material to bounce back after being disturbed
What is elasticity?
A 60 kg student running at 3.0 meters per second has a kinetic energy of?
a)180 J
b)270 J
c) 540 J
d) 8100 J
What is b) 270 J?
spring constant
Newton per meter
A 20 kg object strikes the ground with 1960 J of kinetic energy after falling freely from rest. How fast is the object moving right before it hits the ground?
14 m/s
In a closed system, energy cannot be created or destroyed, but instead will transfer to different types of energy
What is the Law of Conservation of Energy?
As an object falls freely near the Earth's surface, the loss in gravitational potential energy of the object is equal to its
a)loss of height
b)gain in kinetic energy
c)loss of mass
d)gain in velocity
What is b) gain in kinetic energy?
Which of the following is equivalent to 1 Joule?
a) kg m/s2
b) kg m2/s
c) kg m2/s2
d) N s
What is
c) kg m2/s2
An object moving at a constant speed of 25 meters per second possesses 450 J of Kinetic Energy. What is the objects mass?
1.4 kg