The observer in the moving truck sees the ball travel in a vertical path when thrown upward. The Earth-based observer sees the ball's path as a parabola. Figure 38.1 Two observers watch the path of a thrown ball and obtain different results.

In a certain particle accelerator, a proton has a kinetic energy that is equal to its rest energy. What is the speed of the proton relative to the accelerator? 0.87 c 0.25 c 0.75 c 0.71 c 0.50 c

1. Taking north as positive and south as negative for all reference frames, suppose Mayor Adams is riding a southbound train to New York City traveling at 40 m/s relative to the ground, while Governor Hochul is riding a northbound train to Albany at 33 m/s relative to the ground. A) What is the velocity of Mayor Adams in Governor Hochul's reference frame (i.e. in the reference frame where Governor Hochul isn't moving)? B) What is the velocity of Governor Hochul in Mayor Adams reference frame? C) To his surprise Mayor Adams observes a groundhog running along the aisle towards the back of the train with a speed of 2 m/s relative to the train. What is the velocity of the groundhog in Governor Hochul's reference frame? D) What is the groundhog's velocity in the reference frame of someone standing at the train station? E) What is its velocity in Mayor Adams's reference frame? F) What is its velocity in the groundhog's frame? 30 10 ft. 5 ft. 15 ft.

4. The speed for vehicles is typically given in reference to the medium it travels on or through. For example, a car with a top speed of 180 mph is going that speed relative to the ground [in the "ground frame"], while a ship with a top speed of 30 mph is going that speed relative to the water [in the "water frame"], and an airplane with a top speed of 700 mph is going that speed relative to the air [in the "air frame"]. The velocities of these 1.5km objects becomes more complicated when the medium they move through is itself moving, so a plane at top speed subject to a 100 mph tail wind still travels at 700 mph relative to the air, but is going 800 mph relative to the ground. Suppose, when spring arrives, you want to kayak from Bard to the opposite shore of the Hudson, which is 1.5 km due west if you travel the shortest distance across. Your kayaking speed, relative to the water is 0.5 m/s (shore frame) 1.0 m/s, but the river is flowing due south at 0.5 m/s relative to the shore. A)…