91影视

According to Bob on Earth, Planet Y (uninhabited) is 5 ly away. Anna is in a spaceship moving away from Earth at 0.8c. She is bound for planet Y to study its geology. Unfortunately, Planet Y explodes. According to Bob.This occurred 2 yr after Anna passed Earth. (Bob. of course. has, to wait a while for the light from the explosion to arrive, but he reaches his conclusion by 鈥渨orking backward鈥�) Call the passing of Anna and Bob time zero for both. (a) According to Anna, how far away is Planet Y when it explodes? (b) At what time does it explode?

Anna is on a railroad flatcar moving at 0.6c relative to Bob. (Their clock's read 0 as Anna鈥檚 center of mass passes Bob's.) Anna鈥檚 arm is outstretched in the direction the flatcar moves, and in her hand in a flashbulb. According to the wristwatch on Anna's hand, the flashbulb goes off at 100 ns. The time of this event according to Bob differs by 27 ns. (a) Is it earlier or later than 100 ns? (b) How long is Anna's arm (i.e., from her hand to her center of mass.)?

Anna and Bob are In identical spaceships, each 100 m long. The diagram shows Bob's, view as Anna's ship passes at 0.8c. Just as the backs of the ships pass one another, both clocks.there read O. At the instant shown, Bob Jr., on board Bob's ship, is aligned with the very front of Anna's ship. He peers through a window in Anna's ship and looks at the clock. (a) In relation to his own ship, where is Bob Jr? (b) What does the clock he sees read?

The diagram shows Bob's view of the passing of two identical spaceship. Anna's and his own, where ${\mathbf{纬}}_{\mathbf{v}}\mathbf{=}\mathbf{2}$. The length of either spaceship in its rest frame is . What are the readings on Anna', two unlabelled clocks?

According to an observer at Earth's equator, by how much would his clock and one on a satellite in geosynchronous orbit differ in one day? (Geosynchronous orbit means an orbit period of one day-always in the same place in the sky)

Appearing in the time-dilation and length-contraction formulas, ${\mathit{纬}}_{\mathbf{v}}$ , is a reasonable measure of the size of relativistic effects. Roughly speaking, at what speed would observations deviate from classical expectations by 1 %?

Through a window in Carl's spaceship, passing al 0.5c, you watch Carl doing an important physics calculation. By your watch it takes him 1 min. How much time did Carl spend on his calculation?

A pole-vaulter holds a $16\text{ft}$ pole, A barn has doors at both ends, $10\text{ft}$apart. The pole-vaulter on the outside of the barn begins running toward one of the open barn doors, holding the pole level in the direction he's running. When passing through the barn, the pole fits (barely) entirely within the barn all at once. (a) How fast is the pole-vaulter running? (b) According to whom-the pole-vaulter or an observer stationary in the barn--does the pole fit in all at once? (c) According to the other person, which occurs first the front end of the pole leaving the bam or the back end entering, and (d) what is the time interval between these two events?

Bob is watching Anna fly by in her new high-speed plane, which Anna knows to be $\mathbf{60}\mathit{m}$in length. As a greeting, Anna turns on two lights simultaneously, one at the front and one at the tail. According to Bob, the lights come $\mathbf{40}\mathbf{}\mathit{n}\mathit{s}$apart.

(a) Which comes on first?

(b) How fast is the plane moving?

You are on a high-speed train, travelling at a decent clip: 0.8C . On the ground are two signal stations 5km apart, each with a status-reporting sign, which always give simultaneous reports. At precisely noon on the train鈥檚 clocks, the conductor at the front of the train passes one station and sees a sign reading 鈥淎ll clear,鈥� and another employee at the back passes the other station and sees a sign reading 鈥淪evere Electrical Storms Reported! Slow to 0.1c !鈥� (a) How long is the train? (b) Should it slow down? (c) Suppose that both reporting signs display the time very precisely, updated every microsecond. By how much would the two observed time readings differ, if at all?