Work
Energy
Energy Calculations
Power/Units
Toss Up
100
In which of the following scenarios is NO work done?
A. a person pushes a box across the floor
B. a person picks up a bag of groceries
C. a person pushes on a car to get it out of the ditch, but the car doesn't move
D. a person grabs the leash of a dog running away from it
C. the car didn't move.
100
Friction converts kinetic energy into this type
Thermal
100
Calculate the kinetic energy of a 0.135 kg baseball thrown at 40 m/s.
108 J
100
What are two units of power?
Watts and Horsepower
100
What is the energy conversion that occurs in a glow stick?
Chemical to Electromagnetic (light)
200
When will the sign of work done be negative?
When the force on an object and the direction an object is moving are in opposite directions. (Slowing an object down)
200
Type of energy involved when weighing fruit on a scale at the grocery store
Elastic Potential Energy
200
What is the gravitational potential energy of a 1.0 kg mass that is 1.0 m above the ground?
9.8 J
200
Describe two ways to increase your power output. Be specific.
1. Do more work by moving something farther or using a greater force
2. Do work faster
200
Give an example of a device that converts electrical energy to electromagnetic energy?
Lamp
Microwave
tanning bed
300
A construction worker pushes a wheelbarrow 5.0 m with a horizontal force of 50 N. How much work is done?
250 J
300
What is the term for the sum of the kinetic and potential energy of a system
mechanical energy
300
How much elastic potential energy is stored in a bungee cord with a spring constant of 10.0 N/m when the cord is stretched 2.0 m?
20 J
300
There is a trade off when you use more power. You might get something done faster, but you also use more _______.
Energy
300
What happens to the total energy of a frictionless pendulum as it swings back and forth?
It remains constant
400
A man does 400 J of work lifting a box 0.50 m. How much force did the man use to lift the box?
800 N
400
If the mass hanging from a spring was doubled, by what factor would the elastic potential energy change by?
0 - elastic potential energy is NOT related to mass
400
How fast is a car moving if it has 150,000 J of kinetic energy and a mass of 2,000 kg?
12.2 m/s
400
Give an appropriate unit for each measurement:
1. Force
2. Energy
3. Work
4. Velocity
1. N
2. J
3. J
4. m/s
400
The pendulum has a mass of 2 kg. What is the height the pendulum goes to at points 1 and 4?
0.306 m
500
1. Describe two ways that you can do more work when when lifting weights.
2. Give another possible unit for work
1. Lift heavier weights
2. Do more reps
W = F x d = Nm
500
Name three types of non-mechanical energy.
thermal, chemical, electrical, electromagnetic (light)
500
Placing a mass on a scale causes the spring to be compressed by 3.5 cm and creates 0.250 J of elastic energy. Calculate the spring constant (k) of the spring?
408.2 N/m
500
Identify the measurement for each of the following units:
1. m/s2
2. kg
3. N
4. cm3
5. m
6. W
1. acceleration
2. mass
3. Force
4. volume
5. distance
6. power
500
What is the roller coaster's velocity at point C?
23.5 m/s