Question

Sarah and her friends the swim team are playing on the high dive. One of Sarah's friends throws her back pack, containing her swim supplies, into the pool from the high dive platform. The back pack weighs 50 N. When the back pack hits the water, it encounters a 50.0 N upward resistance force. The swim coach, who also happens to be the physics teacher says: "This is a great opportunity to discuss the forces exerted on Sarah's back pack!"
Several students in the group made comments to the Coach about the back pack. Which student has the correct analysis of the forces and motion of the back pack?


A) Once the back pack hits the water, the forces are balanced and the back pack will stop moving.
B) The upward force of the water on the back pack is less than the downward pull of gravity. The back pack accelerates until it reaches the bottom of the pool.
C) Once the back pack hits the water, the forces are balanced (50 N down and 50 N up). But when the back pack hits the water, it stops accelerating; it does not stop moving.
Eliminate
D) Upon hitting the water, the back pack will accelerate upwards because the water applies an upward force. The forces are unbalanced; the upward force is greater than gravity.

Answer 1

Answer: The answer is C:Once the back pack hits the water, the forces are balanced (50 N down and 50 N up). But when the back pack hits the water, it stops accelerating; it does not stop moving.

Explanation: