A75-kg box rests on a horizontal surface. the coefficient of static friction between the box and the surface is 0.30, and the coefficient of kinetic friction is 0.20.
what horizontal force must be applied to the box to cause it to start sliding along the surface?

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