Question

A 0.15-kg ball is traveling at a speed of 20 m/s. How much work must be done on the ball to stop it?

Answer 1

To stop a ball with a mass of 0.15 kg traveling at 20 m/s, 30 Joules of work must be done. This is determined by calculating the initial kinetic energy of the ball using the formula
`KE = 1/2 m v^2`.

Step-by-step explanation:

To stop a 0.15-kg ball that is traveling at a speed of 20 m/s, the work that must be done on the ball can be calculated using the work-energy principle. This principle states that the work done on an object is equal to the change in its kinetic energy. Since the ball is going to stop, its final kinetic energy will be 0 J.

The initial kinetic energy (KE) of the ball can be found using the formula
`KE = 1/2 m v^2`, where m is the mass and v is the velocity. Substituting the given values:
`KE = 1/2 * 0.15 kg * (20 m/s)^2 = 30 J`. Therefore, to stop the ball, 30 J of work must be done in the opposite direction of the ball's motion.

Answer 2

30 J

Step-by-step explanation:

We need enough work to stop the ball, that is, to let its kinetic energy be 0.

Generally, one must study all forms of energy present in the problem. In this case, we only have kinetic one, therefore the total energy is:

Ek = 1/2 m * v^2 = 1/2 * 0.15 kg * (20 m/s)^2 = 30 J

To stop the ball, we need it to be 0, therefore we need exactly 30 J of work