Download 1. An 80 kg water skier is being pulled by a boat with a force of 220

Unbalanced Force Review
Name _____________________________
1. An 80 kg water skier is being pulled by a boat with a force of 220 N causing the skier
to accelerate at 1.8 m/s2. Find the drag force on the skier.
2. A 2000 kg car is slowed down uniformly from 20 m/s to 5 m/s in 4 seconds. Determine
the average net force on the car during this time, and how far the car traveled while
slowing down.
3. Some baseball pitchers are capable of throwing a fast ball at 100 mi/hr. The pitcher
achieves this speed by moving his arm through a distance of 1.5 m. Determine the
average net force that must be exerted on the 0.15 kg ball during the pitch. (1 mile = 1600
meters)
4. After falling from rest at a height of 30 m, a 0.50 kg ball bounces upward, reaching a
height of 20 m. The contact between the ball by the ground lasted 2 milliseconds. Find
the average force exerted on the ball by the ground.
5. What is the normal force on a 75 kg man in an elevator that goes from moving down
at 6.0 m/s to zero in 2.0 s?
6. A helicopter holding a 90. kg box suspended from a rope 5.0 m long accelerates
upward at a rate of 2.1 m/s2. Air resistance is negligible.
a. Draw and label a force diagram for the box.
b. Determine the tension in the rope.
c. At the moment that the upward velocity of the helicopter is 12 m/s, the rope is cut.
The helicopter from then on accelerates upward at 2.5 m/s2. Determine the distance
between the helicopter and the package 3.0 seconds after the rope is cut.
6. A crane is used to hoist a load of mass m1 = 500 kg. The load is suspended by a cable
from a hook of mass m2 = 50 kg, as shown above. The load is lifted upward at a constant
acceleration of 2 m/s2.
7.
hill is at a 35˚ angle.
skier’s mass is 60 kg.
coefficient of friction is 0.08
determine the acceleration of the skier.
8. A 20 kg block (A) rests on a frictionless table; a cord attached to the block extends
horizontally to a pulley at the edge of the table. A 10 kg mass (B) hangs at the
end of the cord.
a) Clearly draw and label the force vectors acting on
each object.
b) Calculate the acceleration of the block and mass.
c) Calculate the tension in the cord.
9. What kind of motion does a constant unbalanced force cause? What is the
experimental evidence of your answer?
10. What is the relationship between acceleration and mass if the unbalanced force is
kept constant? What effect does doubling the mass in this situation have on the
acceleration?
11. What is the relationship between acceleration and net force if the total mass of a
system is kept constant? What effect does tripling the net force on a mass have on the
acceleration?
12. Why is it important to say unbalanced force equals mass times acceleration instead of
force?
13. What does the graph of velocity vs. time look like for an object experiencing a
constant unbalanced force? Repeat for the graph of acceleration vs. time.