An observer is stationary in the inertial system S. A car is moving in the x- direction with speed v = c / √2 with respect to the observer in S. The driver of the car is stationary with respect to the car, and thus the driver is in a different inertial frame S′. The passenger of the car takes out a baseball, opens the sunroof of the car and throws out the ball with a velocity vB =c/√2. If the baseball is thrown in the x-direction (in the same direction the car is moving), what is the speed of the baseball as seen by the observer in S?

An observer is stationary in the inertial system S. A car is moving in the x- direction with speed v = c / √2 with respect to the observer in S. The driver of the car is stationary with respect to the car, and thus the driver is in a different inertial frame S′. The passenger of the car takes out a baseball, opens the sunroof of the car and throws out the ball with a velocity vB =c/√2. If the baseball is thrown in the x-direction (in the same direction the car is moving), what is the speed of the baseball as seen by the observer in S?