8th Grade Science - Work, Machines and Energy

Work is the result of a transfer of ____________ to an object.
In order for work to occur when a force is applied to an object, the object must move::
1. in the opposite direction of the force's direction
2. in a direction that is at right angles to the force's direction
3. in a direction that is in the same direction as the force's direction
Work can be calculated by which equation?
1. W = F/d
2. W = F x d
3. W = d / F
4. F = W x d
If force is measured in Newton’s, and distance is measured in meters, what unit of measure would result in calculating the Work done?
Which equation is used to calculate Power?
1. P = W x t
2. P = t / W
3. P = W / t
The unit which expresses Power as Joules per second is called the ________.
A device that can be used to change the size and/or the direction of a force is called a ____________.
What is the correct definition of the output force of a machine?
1. the product of the input force and the distance through which the input force is exerted
2. the product of the input force and the distance through which the output force is exerted
3. the product of the output force and the distance through which the input force is exerted
4. the product of the output fore and the distance through which the output force is exerted
If the input force to a machine is 400 Newtons, and the output force is 40 Newtons, what is the machine's Mechanical Advantage?

Give your answer as a decimal.
A good machine will produce more work output than work input.
1. True
2. False
The work output of a machine is 200 joules. If the work input of this machine is 400 joules, what is the mechanical efficiency of this machine?
1. 50%
2. 50 percent
A simple machine that consists of a bar that pivots at a fixed point called a fulcrum is a ____________ .
Which of the following is NOT a simple machine.
1. a third class lever
2. a knife
3. a block and tackle
4. a manual hedge trimmer
5. a screw
__________ is the capacity to do work.
If an object is moving, it has ____________ energy.
Energy is expressed in units of _______________.
Which equation can be used to calculate an objects kinetic energy?
An object that weighs 250 Newtons is 100 meters above the ground. What is its gravitational potential energy?

___________ J
An object has 36 J of kinetic energy and 28 J of potential energy. What is its mechanical energy?

_______ J
Which types of energy below are forms of potential energy?

Check all that apply.
1. Thermal energy
2. Chemical energy
3. Electrical energy
4. Sound energy
5. Light energy
6. Energy stored in atoms
Your clock radio is an example of a device that converts electrical energy to;

Select all that apply
1. chemical energy
2. light energy
3. sound energy
4. gravitational potential energy
You through a ball straight up into the air. Which statements below are true when the ball reaches its maximum height.?

Check all that apply.
Which of the following is true about the law of conservation of energy.

Check all that apply.
1. Energy can be created in certain processes.
2. Energy can be transformed from one form to another.
3. Energy can be destroyed in certain processes.
4. The total amount of energy in a closed system is always the same.
The force of _____________ can cause energy in a moving object to be converted into thermal energy.
According to the law of conservation of energy, a perpetual motion machine is:
1. possible to build
2. impossible to build
Resources that can be naturally 'replaced' at the same rate that they are used are called __________ resources.
The principal source of energy for solar, wind and biomass energy is the ________.
____________ is a measure of the average kinetic energy of the particles in an object.
The lowest temperature on the Kelvin scale is:

(Check all that are correct.)
1. - 459 degrees F
2. 0 ºC
3. 32 ºF
4. 0 ºK
Which is the correct equation to convert from Celsius to Fahrenheit?
1. ºF =(5/9 ºC) + 32
2. ºF =(5/9 ºC) - 32
3. ºF = (9/5 ºC) - 32
4. ºF = (9/5 ºC) + 32
On the Kelvin scale, the theoretical temperature at which all molecular motion stops is _____________________.
Concrete highway slabs that increase in size in hot weather, and balloons that increase in size when the air inside them is heated are both examples of ________ ___________. (two words)
Heat is:
1. the energy contained in two objects.
2. the energy transferred between two objects that are at the same temperature.
3. the energy transferred between two objects that are at different temperatures.
4. the same as thermal energy.
The transfer of thermal energy from one substance to another through direct contact is called _________ _______ (two words).
The heat from the sun is transferred to the Earth by means of ______________.
The reason why the ocean next to coastal areas tend to have a cooling effect in the summer is that water has a ________ specific heat than the land next to it.
1. higher
2. lower
The equation that calculates the amount of heat required to raise the temperature of an object is:
1. Heat = (object's specific heat X objects mass) / change in object's temperature
2. Heat = object's specific heat X object's mass X change in object's temperature
3. Heat = object's specific heat / (object's mass X change in object's temperature
During a change of state in matter, it is possible for the temperature of the object to stay the same even though energy is being added to the object.
1. True
2. False
The instrument used to measure heat is the _________.
1. thermometer
2. barometer
3. calorimeter
4. altimeter
In colder climates, home builders use ______________ to reduce the transfer of heat from inside the house to the outside.
Which of the following machines are heat engines?

(Check all that apply.)
1. steam engine
2. electric motor
3. internal combustion engine
4. battery powered watch
5. water driven mill
During which stroke in a four stoke internal combustion engine is the fuel ignited?
1. intake
2. compression
3. power
4. exhaust
A refrigerator works by:
1. transferring thermal energy from outside the refrigerator to inside the refrigerator.
2. moving liquid refrigerant from a high-pressure area to a low-pressure area thus reducing its temperature.
3. using a compressor to expand the refrigerant gas and lower its temperature.
4. using condenser coils to transfer thermal energy from the coils to the refrigerant.