1. A car is driven at constant velocity along a level highway. Indicate the value of the net force and list all the main forces acting on the car to produce the net force. Clearly explain what produces or exerts each of the contact forces acting on the car and explain which forces are balanced. 

2. Summarize two observations that are contrary to the predictions based on Newton's laws but that confirm Einstein's explanation of gravity. Indicate how the predictions based on Newton's theory differ from Einstein's.