Extra Problem 1. In your introductory physics classes, you almost always used the Earth as the reference frame when working problems. Is the Earth an inertial reference frame? Give reasons for your answer. Extra Problem 2. A bus is moving at a constant speed of 15.0 m/s along a straight, narrow road. Let S be the reference frame attached to Earth and S' be the reference frame attached to the bus. Take the x and x' axes to be coincident along the road, such that the bus is traveling in the positive x (and x') direction. A ball is rolled from the back of the bus to the front of the bus, a distance of 8.00 m, with a constant speed relative to the bus of 6.50 m/s. (a) Compute how long it takes the ball to travel from the back of the bus to the front of the bus in S'. (b) How far does the ball travel in S? (c) What is the ball's velocity in S? (d) Compute how long it takes the ball to travel from the back of the bus to the front of the bus in S. Extra Problem 3. A bus is moving at a constant speed of 20.0 m/s along a straight, narrow road. Let S be the reference frame attached to Earth and S' be the reference frame attached to the bus. Take the x and x' axes to be coincident along the road, such that the bus is traveling in the positive x (and x') direction. A ball is rolled from the front of the bus to the back of the bus, a distance of 10.0 m, with a constant speed relative to the bus of 4.00 m/s. (a) Compute how long it takes the ball to travel from the front of the bus to the back of the bus in S'. (b) How far does the ball travel in S? (c) What is the ball's velocity in S? (d) Compute how long it takes the ball to travel from the front of the bus to the back of the bus in S.