# Thread: Acceleration Due to Gravity on Middle Earth

1. I'm working on a physics video project, and I was just wondering if someone could look it over and make sure I did everything right.

The instructions were to find a movie clip and design two problems.

This is my video. The problem I'm designing is "What is the acceleration due to gravity on Middle Earth?"

In the video it takes him 8 seconds to fall. He spins full body length 5 times, and through pausing and taking screen shots, I've determined that the entire tower is roughly 20 times his height. I looked up Christopher Ian's height online and found 6'5".

My math for the height of the video.
6(12)+5=77 inches. 77in(20)= 1540 inches 1540/12= 128.3 ft.
128.3 ft converted to meters is 39.1 m.

I then used to formula (change in distance)=(initial velocity)(time)+(1/2)(acceleration)(time squared)

I set the initial velocity as 0. 39.1=0x8+.5a(64)

I came up with 1.22 m/s.

Does it look like I did everything right on this problem?

And I was wondering if anyone had any ideas for what I can do on the second problem. I was thinking about trying to calculate the final velocity. (change in velocity)=(distance)/(time). Because if the initial velocity is 0, the change would be the final velocity. But I'm not sure if it would work out right.

So if you can look over the problem, or if you have any ideas, thank you.

2.

3. Originally Posted by Skara
I'm working on a physics video project, and I was just wondering if someone could look it over and make sure I did everything right.

The instructions were to find a movie clip and design two problems.

This is my video. The problem I'm designing is "What is the acceleration due to gravity on Middle Earth?"

In the video it takes him 8 seconds to fall. He spins full body length 5 times, and through pausing and taking screen shots, I've determined that the entire tower is roughly 20 times his height. I looked up Christopher Ian's height online and found 6'5".

My math for the height of the video.
6(12)+5=77 inches. 77in(20)= 1540 inches 1540/12= 128.3 ft.
128.3 ft converted to meters is 39.1 m.

I then used to formula (change in distance)=(initial velocity)(time)+(1/2)(acceleration)(time squared)

I set the initial velocity as 0. 39.1=0x8+.5a(64)

I came up with 1.22 m/s.

Does it look like I did everything right on this problem?
It looks all right to me, except the units of acceleration are meters per second per second.

And I was wondering if anyone had any ideas for what I can do on the second problem. I was thinking about trying to calculate the final velocity. (change in velocity)=(distance)/(time). Because if the initial velocity is 0, the change would be the final velocity. But I'm not sure if it would work out right.

So if you can look over the problem, or if you have any ideas, thank you.
If you divide the distance by the time you will get the average velocity, not the final velocity.
Try again.

4. I meant that you'd get the change in velocity, and since the initial velocity is zero, wouldn't the answer of (change in distance)/time equal the final velocity? I might be wrong on that, I'm not really sure

But I decided to go with "How long would it take to fall if the Tower of Isengard were on Earth" (with an acceleration due to gravity of 9.8 ).

Thank you for looking it over.

5. Originally Posted by Skara
I meant that you'd get the change in velocity, and since the initial velocity is zero, wouldn't the answer of (change in distance)/time equal the final velocity?
No.
But I decided to go with "How long would it take to fall if the Tower of Isengard were on Earth" (with an acceleration due to gravity of 9.8 ).

Thank you for looking it over.
Don't give up so easily. The answer is very simple, if you understand the definition of acceleration.

6. I still used the first problem, the acceleration due to gravity on Earth was for the second one, I didn't give up. I finished the problem and turned it in today.