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PHY 231 HW5 Newton's third and first law
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HW5 Newton's third and first law Begin Date: 2/10/2015 12:00:00 AM -- Due Date: 2/18/2015 11:59:00 PM End Date: 2/18/2015 11:59:00 PM
Problem 1:
Full solution not currently available at this time.
Given Newton’s First Law of Motion, what do we reasonably expect an object to do given the
following scenarios?
Variable Name
Min
Max
Step
Sample Value
Part (a) An object sits at rest with no unbalanced forces acting upon it. What do we expect this object to do?
Correct MultipleChoice: The object will remain at rest.
Choice Info:
The object will begin to move at a constant velocity.
Credit: 75
Feedback:
In order for an object to go from rest to any velocity, it
must experience an acceleration, which in turn means it
must have an unbalanced force acting upon it. The
statement indicates that the object does not have any
unbalanced force.
Hints:
2 hints available
• What does the first part of Newton’s First Law of
Motion state? If this object is at rest and has no
unbalanced forces acting on it, then what would cause
it to move?
• An object at rest tends to stay at rest unless acted
upon by an unbalanced force.
The object will begin to move at an accelerating
velocity .
Credit: 50
Feedback:
In order for an object to go from rest to any velocity, it
must experience an acceleration, which in turn means it
must have an unbalanced force acting upon it.
None of these answers.
Credit: 50
Feedback:
One of the answers is correct. If an object is at rest and
no unbalanced foreces are acting on it, how would it
begin to move in any way? What would cause the
motion?
Part (b) An object is traveling with a constant velocity with no unbalanced forces acting upon it. What do we expect
this object to do?
Correct MultipleChoice: The object will remain at the same speed, traveling in the same direction.
Choice Info:
The object will slow down and eventually come to
rest.
Credit: 90
Feedback:
If the object speeds up or slows down, it is experiencing
an acceleration, which means an unbalanced force is
acting upon it.
Hints:
1 hints available
• What does the second part of Newton’s First Law of
Motion state? If you have an object in motion with a
constant velocity and there are no forces, what would
cause it to change in any way?
The object will speed up.
Credit: 75
Feedback:
If the object speeds up or slows down, it is experiencing
an acceleration, which means an unbalanced force is
acting upon it.
The object will begin to spin as it slows down.
Credit: 50
Feedback:
If the object begins to moving in a circle or slows down,
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it is experiencing an acceleration, which means an
unbalanced force is acting upon it.
The object will remain at the same speed but change
direction.
Credit: 50
Feedback:
A change in direction, even with no change in speed, is
acceleration and thus only occurs when an unbalanced
force is acting on the object.
None of these answers.
Credit: 25
Feedback:
One of the answers is correct. If you have an object in
motion with a constant velocity and there are no forces,
what would cause it to change in any way?
Part (c) An object sits at rest with an unbalanced force acting on it. What do we expect this object to do?
Correct MultipleChoice: The object will begin to move with an accelerating velocity.
Choice Info:
The object will remain at rest.
Credit: 50
Feedback:
An object at rest stays at rest unless acted upon by an
unbalanced force. This object is acted on by an
unbalanced force.
Hints:
3 hints available
• What does the first part of Newton’s First Law of
Motion state?
• An object at rest stays at rest unless acted upon by an
unbalanced force.
• This object is acted on by an unbalanced force.
The object will begin to move with a constant
velocity.
Credit: 25
Feedback:
If the object has an unbalanced force, this would cause
the object to accelerate.
None of these answers.
Credit: 25
Feedback:
One of the answers are correct. If a force is applied to
the object and nothing is in place to balance that force,
what would keep the object from moving? How would
the object remain stationary?
Problem 2:
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Problem 3:
Problem 4:
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Problem 5:
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Problem 6:
Problem 7:
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Problem 8:
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Problem 9:
Problem 10:
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Problem 11:
Problem 12:
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Problem 13:
Problem 14:
Full solution not currently available at this time.
A toy car is rolling down the ramp as shown in the figure. The car's
mass is m = 1.1 kg and the ramp makes an angle of θ = 11 degrees with
respect to the horizontal. Assume the car is rolling without friction.
Randomized Variables
m = 1.1 kg
θ = 11°
Variable Name
m
t
Min
1
10
Max
2
20
Step
0.1
1
Sample Value
1.1
11
Part (a) Using the coordinate system specified, give an expression for the acceleration of the car in terms of θ, g, and
the unit vectors i and j.
Correct Equation: a = g sin(θ) cos(θ) i - g sin(θ)2 j
Choice Info:
Valid Choices:
i, cos(θ), g, sin(θ), j, g, sin(θ), 2,
Partial Credit Choices with Feedback:
sin(θ) Credit: 75%
Feedback:You have a Trig. error. You should have cos(θ)
instead of sin(θ).
cos(θ) Credit: 75%
Feedback:You have a Trig. error. You should have sin(θ)
instead of cos(θ).
cos(θ) Credit: 75%
Feedback:You have a Trig. error. You should have sin(θ)
instead of cos(θ).
Hints:
2 hints available
• Draw the free body diagram, and write Newton's
second law for the x- and y-directions.
• There will be a component of the normal force in
both directions - so you can eliminate it to solve for
the accelearation.
InValid Choices:
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cos(φ), sin(φ), cos(α), sin
(α), t, α, m, θ, d, β,
Part (b) What is the magnitude of this acceleration in m/s2?
Correct Algorithm: |a| = 9.81*sin(t*3.14159/180)
Choice Info:
|a| = 9.81*sin(11*3.14159/180)
|a| = 9.81*sin(11*3.14159/180)
|a| = 1.872
Buffer + or - 0.05616
Hints:
2 hints available
• Use your answer for part (a), and find the magnitude
of the acceleration.
• You might know this answer already if you have
seen this problem before with another coordinate
system.
Problem 15:
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