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# Throw a pen and measure gravity watch

1. We were given this question on a worksheet last lecture. The question is this:

‘Throw a tennis ball/your pen/some non-dangerous object into the air, straight up (and catch it again), observe its motion. Use your observation to measure the gravitational acceleration due to Earth [6 marks]’

So me and three of other people in this lecture just started discussing it. We started off by saying that it makes no sense, and trying to figure what it means.

In the end we said you would need a ruler to measure how high the object went and a stopwatch to measure time. You would then use s=ut 1/2at^2 where u = 0 and t is half the time measured between throwing and catching.

So that is how we would measure it. But the question says to observe the motion not to measure it?

QM
2. I don’t know why the plus symbol isn’t showing. I type it in and it doesn’t show.

QM
3. (Original post by Quiz Master)
We were given this question on a worksheet last lecture. The question is this:

‘Throw a tennis ball/your pen/some non-dangerous object into the air, straight up (and catch it again), observe its motion. Use your observation to measure the gravitational acceleration due to Earth [6 marks]’

So me and three of other people in this lecture just started discussing it. We started off by saying that it makes no sense, and trying to figure what it means.

In the end we said you would need a ruler to measure how high the object went and a stopwatch to measure time. You would then use s=ut 1/2at^2 where u = 0 and t is half the time measured between throwing and catching.

So that is how we would measure it. But the question says to observe the motion not to measure it?

QM

Well, if you throw the pen up next to a ruler then you can observe how high it goes.
4. (Original post by Relentas)
Well, if you throw the pen up next to a ruler then you can observe how high it goes.
But you can’t ‘observe’ time

QM
5. Bro your teacher is trolling you
6. (Original post by Quiz Master)
But you can’t ‘observe’ time
It doesnt ask you to observe anything except for the motion of the pen, using this you could say:
"as I threw the ball, it gained speed, peaked at (10m) then came down, it's path was similar to a parabola meaning if we measure the time from when the ball leaves the hand to when I catch it again along with the height it both peaks and the height where the ball left the hand then we can find the distance from the peak to when it came back down to my hand,
(peak height - hand height) = distance ball went
0.5(time) = time ball took to go from peak to hand.
then use a=(v-u)/t
(where u=0 as the peak is the turning point and thus speed=0)
(t = 0.5(time ball took from hand to hand))
v=(distance ball went)/(0.5(time ball took from hand to hand))"

Hope this helped as that's all you should need in theory.
7. (Original post by shameful_burrito)
Bro your teacher is trolling you
Do you think this is the kind of lecturer who would troll a class? http://www.hull.ac.uk/Faculties/staf...-Roediger.aspx

QM
8. (Original post by Relentas)
It doesnt ask you to observe anything except for the motion of the pen, using this you could say:
"as I threw the ball, it gained speed, peaked at (10m) then came down, it's path was similar to a parabola meaning if we measure the time from when the ball leaves the hand to when I catch it again along with the height it both peaks and the height where the ball left the hand then we can find the distance from the peak to when it came back down to my hand,
(peak height - hand height) = distance ball went
0.5(time) = time ball took to go from peak to hand.
then use a=(v-u)/t
(where u=0 as the peak is the turning point and thus speed=0)
(t = 0.5(time ball took from hand to hand))
v=(distance ball went)/(0.5(time ball took from hand to hand))"

Hope this helped as that's all you should need in theory.
Thanks, although we used s= ut 1/2 at^2 ?

QM
9. (Original post by Quiz Master)
Do you think this is the kind of lecturer who would troll a class? http://www.hull.ac.uk/Faculties/staf...-Roediger.aspx

QM
Sure looks like it. But since she teaches at Hull I'll let it slide. Even God has once crossed the Mighty gates of Hull
10. (Original post by shameful_burrito)
Sure looks like it. But since she teaches at Hull I'll let it slide. Even God has once crossed the Mighty gates of Hull
Hahaha that’s funny because Hull is a hell hole

QM

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