(4 pts) A bicycle pump has a barrel 65 cm long. On the upstroke, air is drawn into the pump at a pressure of 1 atm. On the downstroke, the air in the barrel is compressed. How long must the downstroke be to increase the pressure of the air in the barrel to 4 atm

Aperson gives a shopping cart an initial push along a horizontal floor to get it moving, and then lets go. the cart travels forward along the floor, gradually slowing as it moves. consider the horizontal force(s) on the cart while it is moving forward and slowing. which of the following statements is correct? (a) both a forward and a backward force are acting on the cart, but the forward force is larger. (b) only a forward force is acting which diminishes with time. (c) both a forward and a backward force are acting on the cart, but the backward force is larger. (d) only a backward force is acting, no forward force.