# physics

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Superguy is flying at treetop level near Paris when he sees the Eiffel Tower elevator start to fall (the cable snapped). His x-ray vision tells him Lois LaTour is inside. If Superguy is 1.00 km away from the tower, and the elevator falls from a height of 122.5 m, how long does Superguy have to save Lois, and what must be his average speed?
A) 3.00 s, 333 m/s
B) 5.00 s, 200 m/s
C) 7.00 s, 143 m/s
D) 9.00 s, 111 m/s
E) 10.0 s, 96.0 m/s

• physics - ,

Have you calculated how long it takes the elevator to free fall 122.5 m? That would be a good way to start.

Once you have calculated that time T, the speed required is easy: 1000m/T

One of the choices fits perfectly

• physics - ,

I am really not good at physics. How would I go about finding how long it takes the elevator to fall?
Is it going to have something to do with 9.8m/s?

• physics - ,

H = (1/2)g T^2, so
T = sqrt(2H/g) is the time to fall

yes, it has something to do with g.

People aren't "good at physics" until they try solving the problems.

• physics - ,

H=1/2gt^2
t=sqrt(2h/g)
=sqrt(2*240/9.8)
=6.99sec

speed=d/t
=1000/7
=142.8m/s