Work- Power- Simple Machines- Energy
Energy
1. Energy is the ability to do…?
2. What two things must happen in order for work to be done on an object?
3. Energy and work are expressed in a unit of measure called
Kinetic Energy
1. Kinetic energy is due to the __________of an object.
2. What is the equation for determining kinetic energy
3. What two factors determine kinetic energy?
4. If a Hummer and a motorcycle are going the same speed, which has more kinetic energy?
5. What is the kinetic energy of a 4000 kg elephant running at a velocity of 4 m/s?
Potential Energy
1. Potential energy is due to the ____________ of an object.
2. Gravitational potential energy is the potential energy of an object due to is position and ______ above
the ground.
3. What three factors determine gravitational potential energy?
4. What is the equation for gravitational potential energy?
5. What is the gravitational potential energy of a girl who has a mass of 57 kg and is standing on the edge
of a diving board that is 15.5 m above the bottom of the pool?
6. A 62 kg rock climber descends 35 m from the top of the cliff to the ground. What would be his potential
energy at the top of his jump if he was on planet Mars which has a gravity of 3.7 m/s2?
7. A boulder that weights 1687 N is hanging off of a cliff that is 55 m above the ground. What is the GPE
of the boulder if it is about to fall?
Work/Power
1. When work is done ________ is transferred.
2. What two factors determine the amount of work done on an object?
3. What is the equation for calculating work?
4. If you lift a bag of groceries 3 meters and you use 527 N of force to lift the bag, what amount of work
did you do?
5. Power is the amount of ________ done or ________ transferred in a certain amount of ________
6. What are the two possible equations for calculating power?
7. What is the unit of measure for power?
Machines
1. A machine is a device that makes work _______
2. Three possible things that a machine can do to help with work are change ________ change _______ or
change __________ needed to do the work.
3. The force that you give to a machine is called _________ force.
4. The force that a machine puts on an object is called ___________ force.
5. What is the definition for the mechanical advantage of a machine?
6. What is the equation for calculating mechanical advantage?
7. If a machine has an output force of 875 N and you give the machine 688 N, what is the mechanical
advantage of the machine?
8. What is the equation for calculating mechanical efficiency?
9. What is the mechanical efficiency of a machine that gives 256 J of work and the input work was 300 J?
10. Why is there no machine that is 100% efficient?
11. Draw the three types of levers. What are some common examples of each. Be able to identify lever
types
12. How do pulleys work as simple machines? How can you find the IMA of a pulley system?
Equations:
Work=
Potential Energy =
Power=
MA=
Kinetic Energy =
MA of a Lever=
Practice Problems:
Which of the following statements are true about work? Include all that apply.
a.
b.
c.
d.
e.
Work is a form of energy.
A Watt is the standard metric unit of work.
Units of work would be equivalent to a Newton times a meter.
A kg•m2/s2 would be a unit of work.
Work is a time-based quantity; it is dependent upon how fast a force displaces an object.
Which of the following statements are true about power? Include all that apply.
a.
b.
c.
d.
Power is a time-based quantity.
Power refers to how fast work is done upon an object.
Powerful people or powerful machines are simply people or machines which always do a lot of work.
A force is exerted on an object to move it at a constant speed. The power delivered by this force is the
magnitude of the force multiplied by the speed of the object.
e. The standard metric unit of power is the Watt.
6. Which of the following statements are true about kinetic energy? Include all that apply.
a.
b.
c.
d.
Kinetic energy is the form of mechanical energy which depends upon the position of an object.
If an object is at rest, then it does not have any kinetic energy.
If an object is on the ground, then it does not have any kinetic energy.
The kinetic energy of an object is dependent upon the weight and the speed of an object.
Which of the following statements are true about potential energy? Include all that apply.
a.
b.
c.
d.
Moving objects cannot have potential energy.
Potential energy is the energy stored in an object due to its position.
Both gravitational and elastic potential energy are dependent upon the mass of an object.
The gravitational potential energy of an object is dependent upon the mass of the object.
A 1200 kg car and a 2400 kg car are lifted to the same height at a constant speed in a auto service station.
Lifting the more massive car requires ____ work.
a. less
b. the same
c. twice as much
d. four times as much
e. more than 4 times as much
A platform diver weighs 500 N. She steps off a diving board that is elevated to a height of 10 meters above the
water. The diver will possess ___ Joules of kinetic energy when she hits the water.
a. 10
b. 500
c. 510
d. 5000
e. more than 5000 .
Eddy, whose mass is 65.0-kg, climbs up the 1.60-meter high stairs in 1.20 s. Approximate Eddy's power rating.
An 878-kg car skids to a stop across a horizontal surface over a distance of 45.2 m. The average force acting
upon the car is 7160 N. Determine ... .
a.
b.
c.
d.
the work done upon the car.
the initial kinetic energy of the car.
the acceleration of the car.
the initial velocity of the car.