Two magnets are held apart. Once released, the South Pole of one magnet moves toward the North Pole of another magnet until the magnets collide. How does the graph reflect the changes in energy that occur?

Kinetic energy and velocity are at zero when the magnets are held apart, and both increase rapidly when they are released and move together. Energy stored in the magnetic field decreases.

Explanation:

easy

4 m/s

Explanation:

From the law of conservation of momentum,

Total momentum before collision = Total momentum after collision.

But,

Total momentum before collision = 0 m/s ( Both are at the center of the ice rink before the push).

0 = mv+m'v'

Where m = mass of Jack, m' = mass of Jill, v = final speed of Jack, v' = final speed of Jill

-mv = m'v' Equation 1

make v the subject of the equation

v = m'v'/-m Equation 2

Given:  m = 50 kg, m' = 40 kg, v' = 5 m/s.

Substitute into equation 2

v = -40(5)/50

v = -200/50

v = -4 m/s

Note: The negative sign shows that Jack moves to the left with a speed of 4 m/s

Hence Jack's speed = 4 m/s