Phy 121
Your 'cq_1_11.1' report has been received. Scroll down through the document to see any comments I might have inserted, and my final comment at the end.
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Answer the following based on Newton's Second Law:
• How much net force is required to accelerate a 12 kg mass at 3 m/s^2?
answer/question/discussion: 3m/s^2/12kg=.25N
This would be a / m = Fnet. That's not correct and the units don't work out right.
• What would be the acceleration of a 4 kg mass subject to a net force of 20 Newtons?
answer/question/discussion: 20N/4kg=5m/s^2
• If you exert a force of 20 Newtons on a 10-kg object and it accelerates in the direction of your force at 1.5 m/s^2, then how do you know there are other forces acting on the object besides your own?
answer/question/discussion: because the force would’ve had to been calculated given the acceleration and mass, but the force was already given
• What is the total of all those forces and in what direction does this total act?
answer/question/discussion: my direction, .25N+5m/s^2
.25 N isn't correct (see above note).
You can't add two quantities with different units (e.g., N + m/s^2).
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15 minutes
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cq1_08_2 solution and discussion
The following is a solution to the given problem.
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Simply copy your posted document into a text editor and insert revisions,
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How much net force is required to accelerate a 12 kg mass at 3 m/s^2?
The net force would be
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F = m a = 12 ks * 3 m/s^2 = 36 kg m/s^2 = 36 Newtons.
-
Note that the details of the units calculation are necessary and
important.
What would be the acceleration of a 4 kg mass subject to a net force of 20
Newtons?
A 4 kg mass subject to a 20 N force would accelerate at
-
a = 20 N / (4 kg) = (20 kg m/s^2) / (4 kg) = 5 m/s^2.
-
again not the necessity of unit calculations at every step.
If you exert a force of 20 Newtons on a 10-kg object and it accelerates in
the direction of your force at 1.5 m/s^2, then how do you know there are other
forces acting on the object besides your own?
If a 10 kg object accelerates at 1.5 m/s^2, then the net force on the object
is
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F_net = m a = 10 kg * 1.5 m/s^2 = 15 kg m/s^2 = 15 N.
If your force was the only one acting on the object, then the net force on it
would be 20 N and it would be accelerating at 2 m/s^2, not at 1.5 m/s^2.
What is the total of all those forces and in what direction does this total
act?
If you are exerting a force of 20 Newtons on the object and the net force is
only 15 Newtons, this means that the other forces acting on the object must
total -5 Newtons. That is, there has to be a 5 N force opposing you.
.