Download Energy, Work, and Power

Name
Chapter 9
Class
Period
Energy
Energy, Work, and Power
9.1 Work
W = Fd
W = ΔPE = mgΔh
mΔv 2
W = ΔKE =
2
1. While driving home from work a monkey runs out of gas. The monkey pushes the
€car with a 543 N€force to the nearest gas station some 218 meters away. How much
work does the monkey do pushing the car?€
What are the givens and unknowns?
Write the formula(s) are you using
W =
F=
€
€
d=
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
€
€
a)
2. How much work is done to raise a 1-kg hamburger, 0.3 meters, from the table to
your mouth?
What are the givens and unknowns?
Write the formula(s) are you using
W =
F=
d=
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
1
Name
Chapter 9
Class
Period
Energy
3. A 60-kg monkey climbs a 4-m high flight of stairs in the main mall at Mc Neil High
School. How much work does the monkey do?
What are the givens and unknowns?
Write the formula(s) are you using
W =
F=
€
€
d=
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
€
€
4. A 900-N crate is at rest on the floor. a) How much work is required to pull the crate
6.0-m across the floor if the force of friction acting against the crate is 180 N?
b) How much work is required to lift the same crate 6.0 meters vertically?
What are the givens and unknowns?
Write the formula(s) are you using
W =
F=
d=
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
2
Name
Chapter 9
Class
Period
Energy
9.2 Potential Energy
PE = mgh
W = ΔPE = mgΔh
5. How high will a 0.325-kg ball travel if thrown straight up by a monkey who does
115-J of work on the ball?
€
€
What are the givens and unknowns?
Write the formula(s) are you using
W = ΔPE =
m=
€
€ g=
€
h=
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
6. The average food energy intake for humans is 2000 Calories/day. One dietary
Calorie is equivalent to 4186 J. How high would a 120 lb (54.43-kg) person have to
climb in order to “burn off” all the calories they consume in one day?
What are the givens and unknowns?
W = ΔPE =
m=
€
€ g=
€
h=
€
Write the formula(s) are you using
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
3
Name
Chapter 9
Class
Period
Energy
7. A monkey places a 2.0-kg hammer on the edge of a table 0.40-m above the floor. If
the hammer should fall and just by chance land on the top of a loose nail, how much
work would the hammer do to the nail?
What are the givens and unknowns?
Write the formula(s) are you using
W = ΔPE =
m=
€
€ g=
€
h=
€
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
Doc Fizzix Problem Set • Chapter 9
4
Name
Chapter 9
Class
Period
Energy
9.3 Kinetic Energy
mv 2
KE =
2
mΔv 2
W = ΔKE =
2
8. a) What is the kinetic energy of a 3,000-pound (1,361-kg) Porsche driven by a
monkey, traveling at 40 mph (17.88 m/s)? b) What is the kinetic energy if the speed
of the car is€doubled to 80 mph €
(35.76 m/s)?
What are the givens and unknowns?
Write the formula(s) are you using
KE =
m=
€
€
v=
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
€
€
a)
b)
9. Assume your mass is 150-pounds (68.03-kg). How fast would you have to run in
order to have the same kinetic energy as a 3,000-pound (1,361-kg) Porsche driven by
a monkey traveling 55 mph (24.59 m/s)?
What are the givens and unknowns?
Write the formula(s) are you using
KE =
m=
v=
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
5
Name
Chapter 9
Class
Period
Energy
10. Jamaican sprinter Usain Bolt shocked the world by running the 100-meter dash in
9.58 seconds. Determine Usain’s kinetic energy if his weight was 190 lbs (86 kg).
What are the givens and unknowns?
Write the formula(s) are you using
KE =
m=
€
€
v=
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
Doc Fizzix Problem Set • Chapter 9
6
Name
Chapter 9
Class
Period
Energy
9.4 Conservation of Energy
Ei = E f
PE i + KE i = PE f + KE f + W
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
11. A pendulum is made from a 7.50-kilogram mass attached to a rope connected to the
ceiling of a gymnasium. The mass is pushed to the side until it is at position A, 1.5
€ than its equilibrium position. After it is released from rest at position
meters higher
A, the pendulum moves freely back and forth between positions A and B, as shown
in the diagram below.
What is the total amount of kinetic energy that the mass has as it swings freely
through its equilibrium position? [Neglect friction.]
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
Write the formula(s) are you using
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
7
Name
Chapter 9
Class
Period
Energy
12. A monkey does 0.20 joule of work to compress the spring in a pop-up toy. If the
mass of the toy is 0.010 kilogram, a) what is the maximum vertical height that the
toy can reach after the spring is released? b) How fast was the toy traveling when it
left the table?
Write the formula(s) are you using
What are the givens and unknowns?
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
PE o =
KE o =
€
PE f =
€
KE f =
€
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
8
Name
Chapter 9
Class
Period
Energy
13. A baseball pitcher can throw a baseball at 100 mph (44.70 m/s). If such a pitch had
been directed vertically upwards how height would it have traveled?
What are the givens and unknowns?
Write the formula(s) are you using
PE o =
KE o =
€
PE f =
€
KE f =
€
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
14. A 15-m rope is hanging form a tree branch to the ground. A monkey runs as fast as
it can towards the rope and grab a hold of it. After grabbing the rope, the monkey
raises 2-m above the ground. How fast was the monkey running when he grabbed
the rope?
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
Write the formula(s) are you using
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
9
Name
Chapter 9
Class
Period
Energy
15. A ball starts from rest and rolls down a hill. The height of the hill is not known but
when the ball is 3 meters above the ground it is moving at 5 m/s. a) What is the
total mechanical energy of the ball? b) What was the height of the hill?
Write the formula(s) are you using
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
16. A monkey throws a banana from the roof of a 99-ft (30-m) building with an initial
speed of 10 m/s. a) How much mechanical energy does the banana have on release
and b) what is the speed of the banana as it hits the ground? Dam monkey
Write the formula(s) are you using
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
b)
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
10
Name
Chapter 9
Class
Period
Energy
17. An 80-g (0.08-gk) arrow is fired from a bow whose string exerts an average force of
95 N on the arrow over an 80-cm (0.8 m) distance. What is the speed of the arrow as
it leaves the bow?
What are the givens and unknowns?
Write the formula(s) are you using
W =
€
ΔKE =
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
€
18. A 4-kg block is sitting at rest on a friction free tabletop. A monkey pushes the block
along the table and after the block has moved 8-m, the monkey stops pushing on
the block. At the point the monkey releases the block, the block is traveling at 10m/s, a) how much mechanical energy does the block have and b) how large was the
force applied by the monkey?
What are the givens and unknowns?
Write the formula(s) are you using
W =
ΔKE =
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
11
Name
Chapter 9
Class
Period
Energy
19. A car traveling at 30 mph (13.41 m/s) slams on the brakes in order to avoid an
accident. It takes 45.93 ft (14-m) for the car to come to rest.
a. What will be the stopping distance if the velocity is doubled (60 mph)?
b. What will be the stopping distance if the velocity is tripled (90 mph)?
c. What will be the stopping distance if the velocity is if quadrupled (120 mph)?
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
20. The diagram below represents a 155-newton box on a ramp. Applied force F causes
the box to slide from point A to point B.
What is the total amount of gravitational potential energy gained by the box?
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
Write the formula(s) are you using
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
12
Name
Chapter 9
Class
Period
Energy
21. Frank, a San Francisco hot dog vender, has fallen asleep on the job. When an
earthquake strikes, his 300-kg hot-dog cart rolls down a hill and then up another.
When the cart reaches the top of the hill at point A, its speed is 8.00 m/s. a) How
fast is the hot-dog cart going when it goes up the next hill at point B? b) What is the
total mechanical energy at point B?
Write the formula(s) are you using
What are the givens and unknowns?
PE o =
€
PE f =
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
KE o =
KE f =
€
€
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
13
Name
Chapter 9
Class
Period
Energy
22. An 800 kg rollercoaster had a potential energy of 588,240 J at the top of the first hill.
What is the maximum height of the next hill on the track so that the rollercoaster
can make it to the top if 20,000 J of work is done to overcome friction along the way?
What are the givens and unknowns?
Write the formula(s) are you using
PE o =
KE o =
€
PE f =
€
KE f =
€
W =
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
23. A motor is used as an elevator to lift a 10 N monkey to a height of 4.5-meters. If the
total amount of energy used by the motor is 60 J, how much energy was converted
to heat and sound?
What are the givens and unknowns?
PE o =
KE o =
€
PE f =
€
KE f =
€
W =
€
Write the formula(s) are you using
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
14
Name
Chapter 9
Class
Period
Energy
24. A motor lift a 5 N mass to a height of 3.5-meters. If the total amount of energy used
by the motor is 35 J, how much energy was converted to heat and sound?
What are the givens and unknowns?
Write the formula(s) are you using
PE o =
KE o =
€
PE f =
€
KE f =
€
W =
€
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
Doc Fizzix Problem Set • Chapter 9
15
Name
Chapter 9
Class
Period
Energy
25. A block weighing 40-newtons is released from rest on an incline 8.0 meters above
the horizontal, as shown in the diagram below.
If 50-joules of heat is generated as the block slides down the incline, what is the
maximum kinetic energy of the block at the bottom of the incline?
What are the givens and unknowns?
Write the formula(s) are you using
PE o =
KE o =
PE f =
€
KE f =
€
W =
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
€
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
16
Name
Chapter 9
Class
Period
Energy
26. A 30-kg monkey is sliding down a playground slide that is 2.5-m high. The monkey
comes to the bottom of the slide with a speed of 2.0 m/s. How much energy was
dissipated as heat?
What are the givens and unknowns?
Write the formula(s) are you using
PE o =
KE o =
€
PE f =
€
KE f =
€
W =
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
Doc Fizzix Problem Set • Chapter 9
17
Name
Chapter 9
Class
Period
Energy
9.5 Springs
1
PE = kx 2
2
27. How much energy is stored in a spring with a spring constant of 50N/m when it is
compressed 0.05 m?
€
What are the givens and unknowns?
Write the formula(s) are you using
PE s =
k =
€
€
Δx =
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
€
a)
28. A dart of mass 0.10 kg is pressed into a toy dart gun. The spring is compressed 6.0
cm and has a spring constant of 250 N/m. What is the speed of the dart after the
gun is fired?
What are the givens and unknowns?
Write the formula(s) are you using
PE s =
ΔKE =
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
18
Name
Chapter 9
Class
Period
Energy
29. A toy car has a mass of 2.5-kg. The car is moving along the floor at 2.0 m/s when it
hits a spring attached to a wall. The spring has a spring constant of 32 N/m. How
far will the spring be compressed in collision with the toy car?
What are the givens and unknowns?
Write the formula(s) are you using
PE s =
€
ΔKE =
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
€
30. A 0.01 kg steel ball is loaded into a spring gun pointed straight up. When the
spring is compressed .10 m, the ball reaches a height of 20 meters above the gun.
a) How much energy was stored in the spring gun and b) what is the spring
constant of the gun?
What are the givens and unknowns?
Write the formula(s) are you using
PE s =
ΔPE =
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
19
Name
Chapter 9
Class
Period
Energy
9.6 Power
P=
W
t
P=
ΔE
t
31. A 51-kg monkey climbs a 6-m tall tree in 10-s, how much work does the monkey do
and what is the power
€ output of the monkey?
What are the givens and unknowns?
Write the formula(s) are you using
P =
W = ΔPE =
t=
€
€
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
32. A small electric motor is used to lift a 0.50-kilogram mass at constant speed. If the
mass is lifted a vertical distance of 1.5 meters in 5.0 seconds, what is the average
power developed by the motor?
What are the givens and unknowns?
Write the formula(s) are you using
P =
W = ΔPE =
t=
€
€
b)
€
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
20
Name
Chapter 9
Class
Period
Energy
33. A monkey puts out 50-W of power for 1.0-hour, how much work does the monkey
do?
What are the givens and unknowns?
Write the formula(s) are you using
P =
W =
t=
€
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
34. An 8-kg mass is lifted from the ground using a power of 25-W in 7-seconds. To
what height was the mass lifted?
What are the givens and unknowns?
P =
W = ΔPE =
t=
€
€
Write the formula(s) are you using
€
Substitute the known values and solve.
€
a)
Doc Fizzix Problem Set • Chapter 9
21
Name
Chapter 9
Class
Period
Energy
35. A net force of 25-newtons is applied to a moving cart for 10 seconds and the cart
travels 5 meters. What was the power delivered to the cart?
What are the givens and unknowns?
Write the formula(s) are you using
P =
W =
t=
€
€
Substitute the known values and solve.
€
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
a)
36. A 3,000-pound (1,361-kg) Porsche is at rest and pointed north when the gas pedal
is pressed to the metal. If the car goes from 0-60 mph (26.82 m/s) in 3.7 seconds,
calculate the a) change in kinetic energy and the b) power output?
What are the givens and unknowns?
P =
W = ΔKE =
t=
€
€
Write the formula(s) are you using
€
Substitute the known values and solve.
€
a)
b)
Doc Fizzix Problem Set • Chapter 9
22
Name
Chapter 9
Class
Period
Energy
37. A monkey has bought a piano but lives on the sixth-story (16.0-m) of an apartment
building and needs to get the piano to his flat. The piano will not fit through the
doors into the apartment but will fit through the outside window. The monkey
attaches a rope to the piano and the other end to a 1,750-W motor attached to the
top of the building. How long will it take to lift the 285-kg piano to the monkey’s
flat?
What are the givens and unknowns?
Write the formula(s) are you using
P =
W = ΔPE =
t=
€
€
€
Substitute the known values and solve.
© 2013 Doc Fizzix Products, Saving the world with his knowledge of science
€
a)
Doc Fizzix Problem Set • Chapter 9
23