Pilings are driven into the ground at a building site by dropping a 2250 kg object onto them. What change in gravitational potential energy does the object undergo if it is released from rest 16.0 m above the ground and ends up 1.30 m above the ground ? Change in gravitational potential energy:

A100-watt light bulb illuminates a solar cell. the electricity from the solar cell operates a water pump that delivers 1 watt of power. what is the efficiency of the system?

Which is an example of an exothermic process?

The gun from the crime scene shows tool marks where the serial numbers are ground off. there are also tool marks on the bullets left behind. what information can the tool marks on the bullets and gun provide about the crime? what type of evidence does this information provide, individual or class?