Chapter 4 Problems:
1)
A man pushes
against four boxes,
which rest on a
frictionless surface.
a)
Draw a diagram showing all of the forces acting on
box D.
Label each force with its type and the object
that exerts the force.
This is a “free body diagram”.
b)
Apply the Second Law to create an equation for the
acceleration of box D.
This is the “equation of
motion”.
c)
Repeat (a) and (b) for boxes A, B, and C.
d)
The boxes move together.
Write the equation of
motion for the system of four boxes.
A
B
C
D
F
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2)A 100kg man balances a 50kg box
on his head.
He bends his knees a
bit, and then pushes on the ground
so that he moves a distance of 25
cm as he accelerates to a final
upward speed of 3 m/s
a)
What is the acceleration of the manbox system?
b)
What force does the man exert on the box?
c)
What force does the ground exert on the man?
d)
After the man and box leave the ground….
i.
What is the net force on the box?
ii.
What is the acceleration of the box?
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 Spring '10
 Phys123
 Force, Friction, Friction Force, 0.5 K, 0.7 kg

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