12) A 16.0 kg canoe moving to the left at 12.0 m/s makes an elastic head-on collision with a 4.00 kg raft moving to the right at 6.00 m/s. After the collision, the raft moves to the left at 22.7 m/s. Disregard any effects of the water. Find the velocity of the canoe after the collision.

13) A 4.0 kg bowling ball sliding to the right at 8.0 m/s has an elastic head-on collision with another 4.0 kg bowling ball initially at rest. The first ball stops after the collision. Find the velocity of the second ball after the collision.

14) A 25 kg bumper car moving to the right at 5.0 m/s overtakes and collides elastically with a 35 kg bumper car moving to the right. After the collision, the 25 kg bumper car slows to 1.5 m/s to the right, and the 35 kg bumper car moves at 4.5 m/s to the right. Find the velocity of the 35 kg bumper car before the collision.

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.

If angle "a" is 25°, angle "b" is: a) equal to angle c b) less than angle c c) greater than angle c

What is the role of lenses in microscopy?