Question

If you drop a softball from just above your knee, the kinetic energy of the ball just before it hits the ground is about 1 joule

Answer 1

yes it is one joule 1111

Answer 2

True.

Step-by-step explanation:

The average knee height is about 30% of the height of the body. So, if you are 170 cm tall, the knee height would be 0.30(170cm) = 51cm, which is equivalent to 0.51m if we divided by 100.

Now, the total energy at the initial point is

`U=mgh`

Because it's all potential energy. The softball mass around 0.20kg, using gravity as 9.81, we have

`U=0.20kg(9.81m/s^(2))(0.51m)=1.00062 J`

By the conservation of energy theorem, the energy at the final point is the same as the energy of the initial point. It's important to specifiy that the final point is kinetic energy

`U=K\\U=1.00062 J`

Therefore, the statement is true.