Answer:
<em>The average speed of the train is 45 km/h</em>
Explanation:
<u>Speed</u>
It's defined as the distance (d) per unit of time (t) traveled by an object. The formula is:

Let's call x the total distance covered by the train. It covered d1=1/3x with a speed of v1=25 km/h. The time taken is calculated solving for t:



Now the rest of the distance:
d2 = x - 1/3x = 2/3x
Was covered at v2=75 km/h. Thus the time taken is:



The total time is:



Simplifying:

The average speed is the total distance divided by the total time:

Simplifying:

The average speed of the train is 45 km/h
Answer:
that is going at a constant rate
Explanation:
Answer:
l = l0 ( 1 - u^2/v^2) ^0.5
Explanation:
This is the equation of lenght contraction of special relativity
<span>1.37 m/s
Assuming her initial velocity is totally horizontal and her vertical velocity is only affected by gravity, let's first calculate how much time she has until she reaches the ledge 8.00 m below her.
d = 1/2AT^2
8.00m = 1/2 * 9.8 m/s^2 * T^2
Solve for T
8.00 m = 4.9 m/s^2 * T^2
Divide both sides by 4.9 m/s^2
1.632653061 s^2 = T^2
Take square root of both sides
1.277753 s = T
So we now know that she has 1.277753 seconds in which to reach a horizontal distance of 1.75 m. So how fast does she need to be going?
1.75 m / 1.277753 s = 1.369592 m/s
Since we only have 3 significant figures in our data, round the result to 3 figures giving 1.37 m/s</span>