Math
Work & Power
Energy
Systems
Energy Transformations
100
A man pushes his car with a force of 100.0 N through a distance of 20.0 m, how much work does the man do on his car?
2000 J
W = F x d
W = 100 N x 20 m
100
What is defined as the transfer of energy?
Double Points if you can provide BOTH units for it.
Work
Joules (J), Newton-meter (Nm)
100
All forms of energy are measured in ___.
Joules
100
Most systems are which type of system?
DOUBLE POINTS if you can explain why
open
because of resistive forces
100
A radio is an example of what kind of energy transformation?
___ -> ___
electricity to sound
200
How much power is being used by a person doing 20,000 J of work moving tables for 20 seconds?
1000 W
P = W / t
P = 20,000 J / 20 s
200
Is work being done in the picture below? Why or why not?
No because the object does not move
200
When calculating gravitational potential energy, what is the value AND units of "g"?
9.8 m/s2
200
Which type(s) of system allows matter to be exchanged with the surroundings?
open
200
A match is an example of what kind of energy transformation?
___ -> ___
chemical to heat
300
Calculate the kinetic energy of a 10 kg object moving at 5 m/s.
125 J
KE=1/2mv^2
KE=1/2(10)(5)^2
KE=1/2(10)(25)
300
What is the rate at which a person or object does work?
Double Points if you can provide ALL units for it.
Power
Watts (W), Horsepower (HP), Joules per second (J/s)
300
At which point(s) is the potential energy greater than the kinetic energy?
Points A and B
300
Which type(s) of system allows energy to be exchanged with the surroundings?
open AND closed
300
The ___ energy from the Sun is transformed to ___ energy during photosynthesis so plants can make food.
Light, Radiant, or Electromagnetic
Chemical
400
calculate the gravitational potential energy of a 10 kg object 10 m above the ground.
980 J
GPE = mgh
GPE = 10 x 9.8 x 10
400
In which diagram is more work being done?
Diagram A: 
Diagram B:
Neither. Both diagrams show no work being done because the movement of the object is not in the same direction as the force
400
At which point(s) in the pendulum diagram below does the potential energy equal the kinetic energy?
Point #2
400
A cooler with the lid closed is a close example of which type of system?
DOUBLE POINTS: What type is it really?
isolated
closed
400
A battery is an example of what kind of energy transformation?
___ -> ___
chemical to electrical
500
How many joules of heat are needed to raise 10 g of zinc from 50°C to 60°C?
The specific heat of zinc is 0.39 J/g°C
39 J
Q=mc∆T
Q = 10 x 0.39 x (60-50)
Q = 10 x 0.39 x 10
500
An elevator lifts a 100 N moving box up 3 floors in 30 seconds and it takes the movers 5 minutes to carry an identical box up those same 3 floors.
Which system used more power? Explain your answer.
The elevator because they both did the same amount of work but the elevator did it faster.
500
When an object falls from a shelf, its gravitational potential energy is transformed into kinetic energy.
If the object has 50,000 J of gravitational potential energy, how much kinetic energy will it have when it reaches the ground if there is no air resistance?
DOUBLE POINTS if you can explain why.
50,000 J
because of the law of conservation of energy
500
Can a true perpetual motion machine or isolated system exist?
DOUBLE POINTS: Why or why not?
No
Neither can exist because energy is always transferred to the surroundings. (law of conservation of energy)
500
A power plant is an example of what kind of energy transformation?
___ -> ___
mechanical to electrical