4.2.2 Solving Problems Involving Work and Kinetic Energy

Question 1

Solving Problems Involving Work and Kinetic Energy

Answer 1

• The work-kinetic energy theorem relates work to the change in kinetic energy: or . It is an excellent tool for solving problems involving work and forces.
• It is important to distinguish between the net work done on an object and the work done by a certain force on an object when using the work-kinetic energy theorem

Question 2

A typical grade school pitcher can throw a baseball at 80 km / h, or approximately 50 mph. However, only a few professional athletes have the strength needed to throw a baseball at twice that speed. Explain why it is so much harder to throw a baseball twice as fast.

Answer 2

It requires K160/K80 = 12800/3200 = 4 times as much kinetic energy to throw a ball at 160 km/h as it does to throw a ball at 80 km/h

Question 3

A bobsled team begins at the top of a frozen track that runs down a hill that is 0.2 km tall. The total length of the track as it winds its way down the hill is 1.2 km. Ignoring friction, how fast is the bobsled moving when it gets to the finish line?

Answer 3

63 m / s

Question 4

A force does 50 J of work on an object at rest with a mass of 4 kg. Which of the following is the final velocity of the object?

Answer 4

5 m / s

Question 5

The work done to accelerate a car from 0 m / s to 40 m / s is _____ times greater than the work done to accelerate it from 0 m / s to 20 m / s?

Answer 5

four

Question 6

Positive work is done on an object with a mass of 2 kg. The velocity of the object increases from 2 m / s to 5 m / s. How much work is done on the object?

Answer 6

21 J