Question

Pushing a grocery cart with a force with a magnitude of 95 N, applied at an angle of 35° down from the cart horizontal, makes the cart travel at a constant speed of 1.2 m/s. What is the frictional force acting on the cart?

Answer 1

`"friction" ~= 78 N`

Explanation:

Since the speed is constant, there is no acceleration. Since there is no acceleration, the net force acting on the cart is zero. In the horizontal direction, there are only 2 forces action on the cart: the horizontal component of the 95 N (in the forward direction)and the friction (in the rearward direction). They combine to form the net force as follows.

`F_"net" = 95 N*cos35^o - "friction"`

Since I said the net force is zero because of constant velocity

`95 N*cos35^o - "friction" = 0`

`"friction" = 95 N*cos35^o = 77.82 N ~= 78 N`

I hope this helps,
Steve