IPC Practice Questions for Chapter 3 and 4
1. A squirrel has a mass of 0.5 kg. What is its weight?
Fg = mg = 0.5 kg × 9.8 N/kg = 4.9 N
2. A boy weighs 400 N. What is his mass?
m = Fg/g = 400 N/9.8 N/kg = 41 kg
Challenge An astronaut has a mass of 100 kg and has a weight of 370 N on Mars.
What is the gravitational strength on Mars?
gMars = Fg/m = 370 N / 100 kg = 3.7 N/kg
1. A couch is pushed with a horizontal force of 80 N and moves a distance of 5 m
across the floor. How much work is done in moving the couch?
400 J
2. How much work do you do when you lift a 100-N child 0.5 m?
50 J
3. The brakes on a car do 240,000 J of work in stopping the car. If the car travels a
distance of 40 m while the brakes are being applied, how large is the average
force that the brakes exert on the car?
6,000 N
Challenge The force needed to lift an object is equal in size to the gravitational force on
the object. How much work is done in lifting an object that has a mass of 5 kg a vertical
distance of 2 m?
W = Fd = mgd = (5 kg)(9.8 N/kg)(2 m) = 98 J
11. If a helicopter's mass is 4,500 kg and the net force on it is 18,000 N upward, what
is its acceleration?
a = Fnet/m = 18,000 N upward/4,500 kg = 4.0 m/s2 upward
12. What is the net force on a dragster with a mass of 900 kg if its acceleration is
32.0 m/s2 west?
Fnet = ma = 900 kg × 32.0 m/s2 west= 28,800 N west
IPC Practice Questions for Chapter 3 and 4
13. A car pulled by a tow truck has an acceleration of 2.0 m/s2 east. What is the
mass of the car if the net force on the car is 3,000 N east?
m = Fnet/a = 3,000 N east / 2.0 m/s2 east = 1,500 kg
Challenge What is the net force on a sky diver falling with a constant velocity of 10 m/s
downward?
If the velocity is constant, the acceleration is zero. Then by the second law, the net force
must be zero.
16. A baseball with a mass of 0.15 kg is moving at a speed of 40.0 m/s. What is the
baseball's kinetic energy from this motion?
120 J
Challenge A 1,500-kg car doubles its speed from 50 km/h to 100 km/h. By how many
times does the kinetic energy from the car's forward motion increase?
The kinetic energy from the car's motion is 4 times as great when that car is moving at
100 km/h than when that car is moving at 50 km/h.