A student pushes a laptop cart down the hallway by applying 20 Newtons force. The student pushes it 10 meters and then stops at the water fountain with the cart and haves a sip of water. While he drinks from the water fountain, what
type of work is being done to the laptop cart.

None.

Explanation:

        causes an object to change its position, i.e. to have a displacement.

        Since the laptop cart is at rest while he stops at the water fountain, no  

       net work done is on the laptop cart.

the first american roller coaster was the mauch chunk switchback railway, built in the mountains of pennsylvania in the mid-1800s. the track, originally built to send coal to a railway, was reconfigured as a "scenic tour."

the answer is c. the lower legs are levers, and the knees are fulcrums. the ankles hold the loads.