Question

A battleship is moving forward at 20 m/s. a cannonball is fired backward from the ship at 100 m/s relative to the ship. if forward is positive, what is the velocity of the cannonball for an observer on a stationary ship next to the battleship?

Answer 1

For an observer on a stationary ship, a cannonball fired backward from a moving battleship at 100 m/s relative to the ship and with the battleship moving forward at 20 m/s, would have a velocity of -120 m/s (which indicates moving backward).

Step-by-step explanation:

The question involves the concept of relative motion in physics. The student asks if a battleship is moving forward at 20 m/s and a cannonball is fired backward at 100 m/s relative to the ship, what is the velocity of the cannonball for an observer on a stationary ship next to the battleship, assuming forward is positive.

To calculate the velocity of the cannonball relative to the observer on the stationary ship, we subtract the velocity of the battleship from the relative velocity of the cannonball. Therefore, the velocity of the cannonball for the observer on the stationary ship is:
Velocity of cannonball relative to stationary ship = (Velocity of cannonball relative to battleship) - (Velocity of battleship)
= (-100 m/s) - (+20 m/s)
= -120 m/s (where negative indicates the direction opposite to the positive forward direction)

The cannonball is observed to move backward at 120 m/s relative to the stationary ship.