A car is moving at a constant speed. If the force generated by the car to push it forward is 8,000 N, what can be said about the force opposing the car’s motion?

1.It is less than 8,000 N and greater than zero.
2.It is exactly 8,000 N.
3.It is greater than 8,000 N.
4.It is zero.

If a rock is thrown upward on the planet mars with a velocity of 12 m/s, its height (in meters) after t seconds is given by h = 12t − 1.86t2. (a) find the velocity of the rock after two seconds. m/s (b) find the velocity of the rock when t = a. 12−3.72a m/s (c) when will the rock hit the surface? (round your answer to one decimal place.) t = s (d) with what velocity will the rock hit the surface? m/s