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

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

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

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

Therefore, the statement is true.

- measure reactants precisely. ( first choice)

- stir to the reaction take place. ( second choice)

- wait patiently until the reaction completes. ( fourth choice)

- make sure to recover as much copper as possible. ( last choice)

layers of the earth affect the waves and these effects are seen on instruiments such as seimometers