Energy Review

Kinetic Energy

100

Define Kinetic Energy

#8 Energy due to an object's motion

200

#1 How much kinetic energy does a ball have if it is moving forward with a speed of 6 m/s and has a mass of 2 kg?

KE = 1/2mv^2.      (0.5)(2 kg)(6 m/s)²

6² = 36.            (0.5)(2 kg)(36 m/s) = 36 J

300

#12 On a swinging pendulum, where would kinetic energy be at its highest?

On the bottom

400

#12 On a swinging pendulum, where would kinetic energy be at its lowest?

At the top

500

#11 Define mechanical energy

The total amount of potential and kinetic energy in a system.

Potential Energy

100

Define Potential Energy

#9 Energy due to an object's position

200

#4 In the potential energy equation (PE = mgh), what does g stand for?

GRAVITY 

300

#12 On a swinging pendulum, where would gravitational potential energy be at its highest?

At the top

400

#12 On a swinging pendulum, where would gravitational potential energy be at its lowest?

At the bottom

500

#21 Define the law of conservation of energy

Energy cannot be created or destroyed, only changed.

Thermal Energy

100

#13 Define temperature

Temperature is a measure of the average kinetic energy of the particles in an object.

200

#17 What is convection?

Convection is the transfer of thermal energy through currents (air or water)

300

#19 What is conduction?

The transfer of thermal energy through touch

400

#18 What is radiation?

The transfer of thermal energy by electromagnetic waves

500

#22 How does friction affect the law of conservation of energy?

Energy is not lost to friction. The energy is changed into thermal energy.

Machines

100

#6 A screw is a modified simple machine. Which simple machine is it?

An inclined plane 

200

#25 Why does adding oil increase a machine's efficiency?

It reduces friction so that the mechanical energy is not changed into thermal energy.

300

#10 If the amount of work does stay the same, but the distance is increased, what will happen to the amount of force - will it increase, decrease, or stay the same?

F = W/d 

It will decrease

400

#5 What are the 2 simple machines found in a pair of scissors?

Levers and Wedges

500

List all 6 simple machines

1. Screw.    2. Wedge.   3. Inclined Plane

4. Wheel and Axle.   5. Pulley.    6. Lever

Math Practice

100

#2 How much work do you do if you lift a 7N bowling ball to a height of 2 meters?

W = Fd

(7 N)(2 m) = 14 J

200

If a light bulb does 100 J of work over 9 seconds, how much power did it generate?

p = W/t

100 J / 9 s = 11.1 W

300

#2 A box weighs 500N. You use a pulley system to lift the crate. Using the pulleys, you only have to use 250N of force to lift the box. What is the mechanical advantage of the pulleys?

MA = F_R / F_E

500N / 250N = 2

400

#23 You put 125 J of work into a machine. The machine is rusty and only does 97 J of work. What is the efficiency of the machine?

e = work out / work in x 100

97J / 125J x 100 = 77.6%

500

#24 You add some oil to the rusty machine and use it again. You put 125 J of work into the machine. It does 118 J of work. Now how efficient is the machine?

e = work out / work in x 100

118J / 125J x 100 = 94.4%