Suppose that a man throws a ball from the front of a train that is moving at 100 km/hr. If he throws the ball forward at 10 km/hr, what is the speed apparent to the man?
Assuming that the wind resistance doesn't blow the ball back in his face, he'd see the ball moving at a relative velocity of 10km/hr, regardless of the speed of the train.
To determine the speed apparent to the man, we need to consider the concept of relative velocity. Relative velocity is the velocity of one object relative to another object. In this case, we want to find the relative velocity of the ball with respect to the man.
To calculate the relative velocity, we subtract the velocity of the train from the velocity of the ball. The ball is moving at 10 km/hr forward, and the train is moving at 100 km/hr forward. Since the ball is thrown forward, we can consider its velocity as positive.
Relative velocity = velocity of the ball - velocity of the train
= 10 km/hr - 100 km/hr
= -90 km/hr
The result of -90 km/hr means that the ball appears to be moving in the opposite direction of the train with a speed of 90 km/hr. So, the speed apparent to the man is 90 km/hr in the opposite direction.