Soap Opera Friction Worksheet
You may do the work on the worksheet or on a separate piece of paper. However, show your
work!
Assume that there is no vertical acceleration!
1. Allison has an incredibly heavy book bag (it has a mass of 25 kg). She is so tired from
carrying it that she has collapsed onto the ground and is pulling it horizontally with a force of
132 N. There is friction acting on the bag, and the coefficient of kinetic friction between the
bag and the ground is 0.43.
a) Draw the situation and label all the forces acting on the bag. (There are four.)
b) Find the force of gravity acting on the bag.
c) Find the normal force.
d) Find the force of kinetic friction.
e) Find the horizontal net force.
f) Find the acceleration of the bag.
2. Rachel decides to help Allison by lifting up on the bag with a force of 45 N. It is not enough
to make the bag move vertically, but it does help.
a) Draw the situation and label all the forces acting on the bag. (There are five now.)
b) Find the force of gravity acting on the bag.
c) Find the normal force.
d) Find the force of kinetic friction.
e) Find the horizontal net force.
f) Find the acceleration of the bag.
3. Sonia is not as nice as Rachel is. She waits until Rachel leaves, pretends to help Allison, but
she really pushes down on the bag with a force of 47 N. (Remember, Rachel has left.)
a) Draw the situation and label all the forces acting on the bag. (There are five.)
b) Find the normal force.
c) Find the force of kinetic friction.
d) Find the horizontal net force.
e) Find the acceleration of the bag.
4. Rachel returns and is furious with Sonia, so she tries to pull Sonia off the bag. Sonia lets go
of the bag, but her foot gets wrapped around the book bag handle. So, all this fighting results
in an additional horizontal force of 4.2 N acting exactly opposite of Allison’s force. Neither
Rachel nor Sonia is applying any vertical force.
a) Draw the situation and label all the forces acting on the bag. (There are five.)
b) Find the horizontal net force.
c) Find the acceleration of the bag.
5. Oliva comes across a 2500-kg elephant sitting in the road. She decides it needs to move, and
she’s the woman for the job. Knowing that the coefficient of static friction between the
elephant and the road is 0.76, she applies enough force to just get the elephant moving.
a) Draw the picture and label all the forces acting on the elephant. (There are four.)
b) Find the normal force on the elephant.
c) Find the maximum static friction between the elephant and the road.
d) When an object just starts to move, we say that the applied force equals the maximum
static frictional force. Find the force that Oliva applies to the elephant.
6. Claire disagrees with Oliva, and loves the elephant where it is. She, with the help of some
nearby circus people, jumps on the elephant’s back, thus applying a downward force of 1050
N to the elephant. Oliva continues to push, applying the same force that she did in question
#5.
a) Draw the picture and label all the forces acting on the elephant.
b) Find the normal force on the elephant.
c) Find the maximum static friction between the elephant and the road.
d) Is Oliva able to move the elephant? Explain.