Hello!
When hydrogen runs out in a star, it can no longer perform nuclear fusion where hydrogen nuclei combine to create helium. This will stop fusion.
Hope this helps!
Given that the space station is free of gravitational force, it is required that it spins an certain speed to acquire centripetal acceleration.
In this case, you want that the centripetal acceleration, Ac, equals g (gravitational acceleration on the earth), becasue this will cause a centripetal force equal to the weight on earth.
The formula for centripetal acceleration is Ac = [angular velocity]^2*R
where R = [1/2]50.0m = 25.0 m
Ac = 9.81 m/s^2
=> [angular velocity]^2 = Ac/R = 9.81m/s^2v/ 25.0m = 0.3924 (rad/s)^2
[angular velocity] = √(0.3924) rad/s = 0.63 rad/s
Answer: 0.63 rad/s
Let
V the speed of the girl per step
v the speed of the escalator per step
L the length between ground and floor in number of steps
V*60+v*60=L => V+v=L/60
V*90-v*90=L => V-v=L/90
By adding the equations V+v=L/60 and V-v=L/90 we get:
2V=L(3+2)/180
V=5L/360
V = L/72
Time to climb (in steps) with v=0 (escalator standing still) is:
V*t=L
t = L/V
t = L/(L/72)
t =72 steps
The girl will count 72 steps.
south = -(north)
Displacement = (4 km north) + (2 km south) + (5 km north) + (5 km south)
Displacement = (4 km north) - (2 km north) + (5 km north) - (5 km north)
Displacement = (4 - 2 + 5 - 5) km north
<u>Displacement = 2 km north </u>
