Free-body diagrams
1. A 10 kg dumbbell resting on a table is partly
supported by a spring that pulls upward with a
force of 50 N.
a. Draw and label the forces on the free-body
diagram.
b. Calculate the weight in newtons and label it
on the free body diagram.
c. If the dumbbell is not moving then the net force on it must be zero. Use this fact to calculate
the support forces. You may assume they are both equal.
d. What force would the spring have to exert to make the support forces exactly zero?
2. For each situation below, an object is at rest with a net force of zero. All forces are shown.
Calculate and label the missing force magnitude.
a.
b.
c.
d.
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3. In each situation below, a 10 kg box is at rest with a net force of zero. Beside each sketch, draw
the free-body diagram for the box. Calculate and label the magnitude of the normal force.
a. The 10 kg box is at rest on the floor.
b. The 10 kg box is pushed down with an applied force of 50 N.
c. The 10 kg box is pulled up with an applied force of 20 N.
d. The 10 kg box is pressed against the ceiling with an applied force of 130 N.
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