Which changes will cause an increase in the magnetic field of a solenoid check alll that apply

What is the most useful equation for electric power?

Students design a model roller-coaster track. they place a rubber ball at the highest point on the track and let it go. the ball rolls along the track pulled only by the force of gravity. eventually, it comes to a stop. which change to the design will result in the ball moving the greatest distance?

Glass has a hardness that is in the middle of the hardness scale. what is the hardness of glass?