Physics question?

Question

A free falling object in the last second has travelled five times the distance it has travelled in its first second. What is the height it is falling from?
Please help cant figure out how to do it!!!

Answer 1

Distance traveled during enth second is given by the formula
S = [g/2] [2n-1].

Distance traveled in the first second is [g/2] ------using n=1.

It is given S / [g/2] = 5. Hence 2n-1 = 5 which implies n = 3

Height of the building is 0.5 g t^2 = 4.9* 9= 44.1m,

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The above formula can be derived as follows.
Distance traveled = average velocity x time.

The velocity at the end of [n-1] second is g [n-1] = ng - g, using v = u +at formula.

After one second, its speed is [ng- g] + g*1 = ng,

Average velocity during this second is
[2ng -g] /2 = [g/2] [2n-1]

Distance traveled during the last one second,
(enth second) is = [g/2] [2n-1] * 1 = [g/2] [2n-1]
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Answer 2

Hi Josh. I will try to walk you through the process of thinking about this question.

Gravity accelerates the object at a rate of 32 ft/sec/sec. If the object 'starts' following from rest, after one second it will have accelerated to 32 ft/sec. Its avg. rate of fall would be (0 + 32)/2 = 16 ft/sec. So, in the first second it will fall 16 ft.

In the next second, it will accelerate from 32 ft per second to 64 ft per second. So, during this, the second second of falling, it will fall at an avg speed of (32 + 64)/2 = 48 ft per sec. At an avg of 48 ft per second it will fall 48 ft.

In the 3rd second the object falls, it falls at an avg speed of (64 + 96)/2 = 80 ft per sec. So, in the 3rd second of falling, it will fall 80 feet.

Notice that 80 feet is equal to 5 x 16 feet. So in the 3rd second of falling the object has fallen five times the distance it traveled in the first second!

So, the object fell for 3 seconds. During the first second it fell 16 ft. During the second second it fell 48 ft. And, during the third second it fell 80 ft for a total of 144 ft!

Hope this helps you. Best wishes and good luck.

Answer 3

hmm so it traveld in two seconds? if so then
0-1 second = h
1-x second = 5h

S = 1/2(9.8)t^2 +0 + 0
6h= 4.9t^2 if time is 2 seconds.. then
h=3.26 m

if it isnt 2 seconds, then just substitute.