What could cause a physical change in a bar of steel

Avoltaic cell converts chemical energy to

While the change in blank will remain the same during a collision, the force needed to bring an object to a stop can be blank if the time if collision is blank

The electric field direction is defined by the direction of the force felt by (select one of the following answers): 1. a negative charge. 2. a positive charge. 3. both positive and negative charges.