Physics Problems: Please just help with first problem I dont understand?

Question

The bus in the previous problems is 70 feet long, according to its passengers and driver. What is its length from your vantage point on a fixed planet?
(The previous problems were:
-A passenger on an interplanetary express bus traveling at v=0.99c takes a five-minute catnap, according to his watch. How long does the nap last from your vantage point on a fixed planet?
and..
-According to Newtonian mechanics, the momentum of the bus in the preceding problem is p=ymv. How does the actual momentum of the moving at 0.99c compare with the momentum it would have if classical mechanics were valid? How does the momentum of an electron traveling at 0.99c compare with its classical momentum)
Please just help with first one

Answer 1

The length transformation of special relativity (the Fitzgerald contraction) is given by

L = L0*√[1-(v/c)^2]

You have v/c = .99, so √[1 - .99^2] = 0.141

The apparent length will be 70*0.141 = 9.875 feet

Answer 2

First calculate the 2nd of inertia. Your e book would desire to have a table of moments of inertia for quite a few shapes. locate the cylinder. the 2nd of inertia will by utilising mass * radius * some extensive type. next calculate the frictional acceleration. (alpha) = (exchange in omega) / time utilising the 1200 rmps in 57 seconds. next calculate the acceleration you will desire to finished: (alpha) = (exchange in omega) / time utilising the 1200 rmps in 3 seconds. upload those accelerations at the same time. Torque = (2nd of inertia)*(sum of alphas) word ON instruments do no longer forget approximately to transform revs consistent with minute to radians consistent with 2nd. 2pi radians in a rev and 60 seconds in a minute. additionally convert centimeters to meters in case you decide on your torque to come back out precise in newton-meters.