A student is explaining the forces pushing on a pencil sitting on a desk. What is the force that pushes a pencil up from where the desk it is sitting on?

Gravity

Rolling friction

Normal friction

Sliding friction

Acar is going 5m/s around a bend with a radius of 10m/s why is the accelerant?

The percent efficiency of a machine can never be 100% (or greater), because in the real world some energy is always converted into a. heat b. work c. input force d. output force

Aball tossed vertically upward from the ground next to a building passes the bottom of a window 1.8 s after being tossed and passes the top of the window 0.20 s later. the window is 2.0 m high from top to bottom. what was the ball's initial velocity? the unit vector j^ is directed upward. how far is the bottom of the window from the launch position? how high does the ball rise above the launch position?