Name
Period
Date
Net Force (Unbalanced Forces) Worksheet 2
1. An elevator is moving up at a constant velocity of
2.5 m , as illustrated in the diagram. Rider Ellie Vator
s
has a mass of 85 kg.
a. Construct a force diagram for Ellie. (Which force is
bigger? How do you know?)
b. Write an equation for the vertical
forces acting on Ellie Vator.
c. Calculate the force the floor exerts on
Ellie.
2. The elevator now accelerates upward at 2.0 m
.
s2
a. Construct a force diagram for Ms.
b. Write a Newton’s 2nd Law net force
Vator. (Which force is bigger? How
equation for the vertical forces acting
do you know?)
on Ellie.
c. Calculate the force the floor now
exerts on Ellie.
d. How does Ellie feel as she accelerates
upward in the elevator? (Lighter,
heavier, or normal?) Why?
Net Force (Unbalanced Forces) Worksheet 2
page 2
3. Upon reaching the top of the building, the elevator accelerates downward at
 3 .0 m 2 .
s
a. Construct a force diagram for Ellie
b. Write a Newton’s 2nd Law net force
Vator. (Which force is bigger? How
equation for the vertical forces acting
do you know?)
on Ellie.
c. Calculate the force the floor now
exerts on Ellie.
d. How does Ellie feel as she accelerates
downward in the elevator? (Lighter,
heavier, or normal?) Why?
4. While descending in the elevator, the cable suddenly breaks.
a. Neglecting any air resistance or other frictional effects, what force does the floor
now exert on poor Ellie Vator?
b. How does Ellie now feel as she free falls in the elevator?
c. Does the force of gravity still act upon Ellie as she free falls? So is she actually
weightless?
d. Suppose Ellie takes an apple out of her purse and releases it in front of her.
What motion will the apple appear to have to Ellie? Why?
Net Force (Unbalanced Forces) Worksheet 2
page 3
5. Consider the situation where Ellie’s brother Darth, who has a mass of 68 kg, is
descending in an elevator at a constant velocity of 4.0 m . At some time "t", the
s
elevator starts to slow to a stop at the rate of 2.0 m 2 .
s
a. Construct, in the margin to the right, a qualitative motion map indicating the
relative positions, velocities and accelerations of Darth as he descends.
b. What is the magnitude of the net force acting on Darth when he is descending
(i) at constant speed?
(ii) As he accelerates?
c. Construct quantitative force diagrams (include magnitudes) for Darth as he
descends
(i) at constant speed.
(ii) During his period of acceleration.
d. If Darth was standing on a bathroom scale calibrated in Newtons, what would the
scale read while he was
(i) descending at constant speed?
(ii) slowing to a stop?

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