Katie pushes on a 10 kg box with 70 N of force, but the box only accelerates by 3 m/s2. How much friction is there? Question 2
If Max does 500 J of work spinning a 10% efficient generator, how much electrical energy will he produce?

Question 3
A 10 kg go-kart driven by a 30 kg boy starts from rest and rolls down a hill of height 10 m.

What is the predicted speed of the boy and go-kart at the bottom of the hill?

Question 4
A man applies 500 N of horizontal force to push a 100 kg wooden crate 20 m across a floor.

What is the work that the man performs upon the crate over the 20 m distance? (Answer in kJ)

Question 5
A man applies 500 N of horizontal force to push a 100 kg wooden crate 20 m across a floor.

When sliding, the crate experiences a friction force of 200 N in the direction opposite its motion. What is the work that the friction does upon the crate over the 20 m distance?

Question 6
A man applies 500 N of horizontal force to push a 100 kg wooden crate 20 m across a floor.

What is the net work done on the crate?

Question 7
A man applies 500 N of horizontal force to push a 100 kg wooden crate 20 m across a floor.

What is the change in the crate’s kinetic energy? (Answer in kJ)

Question 8
A man applies 500 N of horizontal force to push a 100 kg wooden crate 20 m across a floor.

Calculate the efficiency with which the man’s work is turned into the crate’s kinetic energy. (answer in decimal form)

Question 9
A moving hockey stick hits a stationary 160 g hockey puck (m = 0.16 kg) and applies a horizontal force F to the puck. The two objects remain in contact for the first 0.25 m (25 cm) of the puck’s motion. The puck then slides away at a speed v of 20 m/s. What force F is delivered to the puck?

Question 10
A weightlifter grabs a 50 kg barbell resting on the floor, raises it 2 m, then holds it in place.

What is the barbell’s kinetic energy before being lifted?

Question 11
A weightlifter grabs a 50 kg barbell resting on the floor, raises it 2 m, then holds it in place.

What is the barbell’s kinetic energy when the lift is complete?

Question 12
A weightlifter grabs a 50 kg barbell resting on the floor, raises it 2 m, then holds it in place.

What is the barbell’s change in kinetic energy?

Question 13
A weightlifter grabs a 50 kg barbell resting on the floor, raises it 2 m, then holds it in place.

What is the net work done on the barbell?

Question 14
A weightlifter grabs a 50 kg barbell resting on the floor, raises it 2 m, then holds it in place.

How much work does the weightlifter perform on the barbell?

Question 15
Consider a rubber ball which has an efficiency in one bounce of 79%. (That means 79% of the kinetic energy before the bounce remains kinetic energy after the bounce, while the rest of the energy is converted to thermal energy.) If the ball drops from a height of 9 m, then how high does it bounce back on the first bounce?

Question 16
The motor of a 1.8 kg battery-powered toy car creates a constant force of 0.80 N in the direction of motion. If the car starts from rest, then what is its speed after 1.5 m of forward motion? (You may assume no friction.)

Question 17
How much distance does it take to stop a car going 30 m/s (67 mph) if the brakes can apply a force equal to one-half the car's weight?

Question 18
The driver of a 1000 kg car traveling at 12 m/s suddenly sees a stop sign 70 m away. How much force must be applied using the brakes for the car to stop just in time?