Friction: a force between an object and the surface it is moving over Imagine you push a book across an incredibly slippery surface. It slides right across because there is NO friction. Next, you push the same book across a rougher surface that exerts friction.

1.)Will the velocity of the book change as it moves across the surface with NO friction? Explain your answer.

2.)Will the velocity of the book change as it moves across the surface WITH friction? Explain your answer.

Askydiver weighing 140 lb (including equipment) falls vertically downward from an altitude of 19,000 ft and opens the parachute after 18 s of free fall. assume that the force of air resistance, which is directed opposite to the velocity, is of magnitude 0.55|v| when the parachute is closed and is of magnitude 14|v| when the parachute is open, where the velocity v is measured in ft/s. assume that acceleration due to gravity has magnitude 32 ft/s/s; remember that weight is the product of mass and gravitational acceleration. (a) find the speed of the skydiver when the parachute opens. (b) find the distance fallen before the parachute opens. (c) what is the limiting velocity vl after the parachute opens? (d) determine how long the sky diver is in the air after the parachute opens. (e) plot the graph of velocity versus time from the beginning of the fall until the skydiver reaches the ground.

The built in flash in a compact camera is usally capable of giving correct exsposure for distance up to how many meters?

Why do some scientists and archeologists think that volta was not the first person to build a battery