# Hewitt Chap. 35

If you walk 1km/h down the isle of a train that moves 60km/h what is your speed relative to the ground?

61km/h

In the previous question, is your approximate speed relative to the Sun as you walk down the isle of the train slightly more or much more?

much more – 110,000km/h

what hypothesis did G. F. Fitzgerald make to explain the findings of Michelson and Morley?

proposed that the length of the apparatus shrank in the direction in which it was moving by just the amount required to counteract the presumed variation in the speed of light. shrinkage factor equation—-

What classical idea about space and time was rejected by Einstein?

The classical idea that space and time are independent of eachother

Two examples of Einsteins first postulate

All laws of nsture are the same in all uniformly moving frames of reference

No experiment, mechanical, electrical, or optical, has ever revealed absolute motion

No experiment, mechanical, electrical, or optical, has ever revealed absolute motion

one example of Einstein’s second postulate

no matter how fast two observers might be moving relative to each other, each of them would measure the speed of light passing them to be 300,000 Km/s

– speed of light is constant

– speed of light is constant

INside the moving compartment of figure 35.4, light travels a certain distance to the front end and a certain distance t the back end. How do these distances compare as seen in the frame of reference of the moving rocket?

simultaneously

How do the distances in question seven compare as seen from the frame of reference of an observer on a stationary planet?

The distance travelled to light the back is shorter

How many coordinate axes are usually used to describe three-dimensional space? What does the fourth dimension measure?

three – x, y, z, axis

fourth – time

fourth – time

Under what condition will you and a friend share the same realm?

Two side by side observers at rest relative to each other share the same reference frame. – without relative motion between them.

What is special about the ratio of distance traveled by a flash of light and the time it takes the light to travel this distance?

the ratio will always be the same, the speed of light

Time is required for light to travel along a path from one point to another. If this path is seen to be longer because of motion, what happens to the time it takes for light to travel this longer path?

it takes longer

What do we call the stretching of time?

Time dilation

What is an algebraic expression for the Lorent factor y (gamma)? Why is y never less then 1?

1/(1 – v 2/c 2)1/2; v 2/c 2 is always a positive number, so the denominator is less than 1, making the ratio greater than 1.

How do measurements of time differ for events in a frame of reference that moves 50% the speed of light relative to us? At 99.95%?

1.15, 10 x

What is the evidence for time dilation?

varified through the lifetimes of high-speed particle accelerators – increase as the speed goes up – and through not-so-fast motion – Atomic clocks in orbit in the GPS system run slower because they are in orbit.

Short-lived particles travelling at high speeds in particle accelerators live longer.

Atomic clocks flown in jets run slower because they are in motion.

Short-lived particles travelling at high speeds in particle accelerators live longer.

Atomic clocks flown in jets run slower because they are in motion.