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do all five questions

Question 1

20 pts

Ignoring the effects of air resistance, if a ball falls freely
toward the ground, its total mechanical energy

Group of answer choices

increases

remains the same

not enough information

decreases

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Question 2

20 pts

A child jumps off a wall from an initial height of 16.4 m and lands
on a trampoline. Before the child springs back up into the air the
trampoline compresses 1.8 meters. The spring constant of the
elastic in the trampoline is K = 288 N/m. Find the mass of the
child. Report your answer to 1 decimal place. Please show your work
to earn full credit.

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Question 3

20 pts

A 16.0 kg cart is moving with a speed of 14.0 m/s. To what height
up a frictionless hill will the cart roll before starting to roll
back down? Report your answer to 1 decimal place. Please show your
work to earn full credit.

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Question 4

20 pts

An object is thrown upward into the air and follows a parabolic
trajectory. As it moves through the air its potential energy

Group of answer choices

increases, then decreases

stays the same

decreases, then increases

increases only

decreases only

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Question 5

20 pts

An object is thrown upward into the air and follows a parabolic
trajectory. As it moves through the air its kinetic energy

Group of answer choices

decreases, then increases

stays the same

increases only

decreases only

increases, then decreases

Conservation of Energy

Previously, we have looked at how the energy of an object can be
changed by work that is being done to it. In this lesson we will be
looking at a special case of the Work-Energy Theorem.

https://en.wikipedia.org/wiki/Thermodynamics

Closed Systems

Work is done when a force acts on an object over a distance. An
applied force from a person or a friction force is usually easy to
identify, but there can be other forces acting on the object at the
same time that don't affect the particular motion we are interested
in. For instance, a car may be moving on the interstate. We are
interested in the force of friction and the force created by the
engine to get the car moving. The force of gravity is also acting
on the car, but since the car is not dropping into the ground, no
work is done. This goes back to the idea that W=Fxd. Since there is
no change in distance from the ground W=0J.

However, what if we cannot identify any external forces that are
acting on the object? If this is the case, then we have what is
known as a closed system. From an energy perspective, a closed
system means that nothing is adding or removing energy from our
object. If this is true, then the amount of work being done is
equal to zero, and the total amount of mechanical energy will stay
constant. The picture above represents the closed system using the
dotted line to separate the system from the surroundings.

Conservation of Energy

In closed systems energy is conserved. This means no energy is
added or removed from the system. In the pendulum system at left
the potential and kinetic energy is constantly changing, but
overall the total amount of energy is the same at every point in
the system. We can set up problems like this using LOL
charts.

This means that if our kinetic energy increases during the problem,
the potential energy must decrease. If the potential energy
increases, the kinetic energy must decrease. Again, we are not
adding or taking away energy from the object, we are just changing
its form.

Another common example of the idea of conservation of momentum is
the roller coaster. Some work must be done to get the object to the
top of the first hill. If we ignore friction, conservation of
energy is observed. This is why the roller coaster will never be
able to reach a higher position than where it started. It also
means that the coaster will be going the fastest through their
lowest positions.

Example Problem 1

A roller coaster is traveling 40 m/s when it reaches the bottom of
the first hill. How tall must the hill be in order to reach this
velocity?

GPE = KE

LOL Graph

The first step in solving this problem is to determine the starting
and ending situations. The start would be the top of the hill where
the coaster has all GPE. The ending position is at the bottom of
the hill where the coaster has all KE. Ignoring friction, the LOL
graph will look like this. Since this is a closed system, we place
the roller coaster in the circle but there are no arrows coming in
or out of the circle.

Based on the LOL chart we can write the following equations:

GPE = KE

m * g * h = .5 * m * v2

A quick look at this equation tells us that the mass variable is
found on both sides of this equation. This means we can cancel the
m's and rewrite the equation as:

g * h = .5 * v2

Inserting our numbers we get:

9.8 * h = .5 * (40)2

h = 81.6 m tall

It is important to notice that gravity is acting on both objects.
In fact, it is the force of gravity that is responsible for the
motion of both the roller coaster. Gravity is not an external
force. It is always present, and is acting on the object because of
it's own mass. So an object can still experience conservation of
energy if gravity is the force causing the motion or the transfer
of energy.

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Example Problem 2

Starting from rest, a 25 kg child slides down a frictionless slide.
The slide is 3.0 m high. What is the child's speed at the bottom of
the slide?

GPE = KE

LOL Graph

In this situation the child starts at the top of the slide which
means all GPE. At the bottom of the slide the child has all KE.
Notice, the LOL chart looks similar to the one used in Example
1.

Using the LOL chart we know that GPE = KE so:

m * g * h = .5 * m * v2

Canceling the mass gives us:

g * h = .5 * v2

9.8 * 3 = .5 * v2

v = 7.67 m/s

The child's speed at the bottom of the slide is 7.67 m/s.

Example Problem 3

A 755 N diver dives from a board 10.0 m above the water's surface.
If the diver leaves the board with an initial speed of 2.00 m/s,
what is the diver's speed when striking the water?

KE + GPE = KE

LOL Graph

The diver has both PE and KE when leaving the board, so the left
side of the LOL chart will have both. Once the diver hits the
water, there is no more PE. It has all been converted to KE. So the
right side of the equation will only have KE.

Using the LOL chart we know that KE + GPE = KE so:

(.5 * m * v2) + (m * g * h) = .5 * m * v2

Since mass is included in each term of the equation we can still
cancel the mass. This gives us:

(.5 * v2) + (g * h) = .5 * v2

(.5 * 22) + (9.8 * 10) = .5 v2

2 + 98 = .5 v2

100/.5 = v2

200 = v2

v = 14.1 m/s

The diver's speed at the end of the dive is 14.1 m/s.

Example Problem 4

A ball is released from an initial height of 10 m so that as the
ball stops it compresses a spring with 40 cm. The spring constant
is K = 50 N/m. Find the mass of the ball.

GPE = EPE

LOL Graph

Initially, the ball is held above the spring having only GPE. As it
falls, the GPE becomes KE, but the final situation here is after
the ball has stopped. The energy transfer

Therefore, as God’s chosen people, holy and dearly loved, clothe
yourselves with compassion, kindness, humility, gentleness and
patience. Col 3:12

Answer #1

just do questions 5 through 10
3.13.6
Question 110 pts
A 319 kg motorcycle is parked in a parking garage. If the car has
35,494 J of potential energy, how many meters above ground is the
car? Report your answer to 1 decimal place. Please do not include
units or the answer will be marked incorrect.
Flag this Question
Question 210 pts
A box sitting on the top of a hill has 252 J of potential energy.
If the hill...

8 through 10 done please!!
3.13.6
Question 110 pts
A 319 kg motorcycle is parked in a parking garage. If the car has
35,494 J of potential energy, how many meters above ground is the
car? Report your answer to 1 decimal place. Please do not include
units or the answer will be marked incorrect.
Flag this Question
Question 210 pts
A box sitting on the top of a hill has 252 J of potential energy.
If the hill is...

Question 1 (1 point)
Which is not necessary in order to do work on an object (use the
scientific definition of work)?
Question 1 options:
There must be a change in momentum.
A net force must be applied to the object.
The object must undergo a displacement.
A component of the force must be in the direction of motion.
Question 2 (1 point)
The change in gravitational potential energy for a 1.9 kg box
lifted 2.2 m is:
Question 2...

ch 6
1:
It is generally a good idea to gain an understanding of the
"size" of units. Consider the objects and calculate the kinetic
energy of each one.
A ladybug weighing 37.3 mg
flies by your head at 3.83 km/h
.
×10
J
A 7.15 kg
bowling ball slides (not rolls) down an alley at 17.5 km/h
.
J
A car weighing 1260 kg
moves at a speed of 49.5 km/h.
5:
The graph shows the ?-directed force
??...

QUESTION 1
? What is the relationship between family dysfunction and
schizophrenia?
a.
?Research has substantiated a link between family dysfunction
and schizophrenia but can't say which causes the other.
b.
?Family dysfunction is a major causative factor for
schizophrenia.
c.
?Research has failed to substantiate a direct causal link
between family dysfunction and schizophrenia.
d.
?Family dysfunction plays a minor role in developing
schizophrenia.
1.00000 points
QUESTION 2
? Chuck has no life plan; he simply lives from...

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