A Physics Question
July 25th, 2008 at 12:00am | by Christopher
An object accelerates from rest with constant acceleration and covers a distance of x at t = 4 and covers a distance of y at t = 6. Find x:y.
Note that this question was taken from the National Physics Quiz 2007. I got a ratio of 4:9 while the answer states that it should be 9:13. Now, do it for yourself. What do you get? Click the spoiler below to view how I got a 4 : 9.
Now, if anyone could show me by the means of mathematical working why x:y is 9:13 and not 4:9, please post your working below. I would like to learn too. Heh.
Here’s another brainteaser. If ds/dt is velocity and dv/dt is acceleration, what is da/dt?
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Posted in Personal
u=0 t=4 and 6
Assuming acceleration = 10ms²
Only equation that can be used is s=ut + 1/2at²
For t=4
s=(0)(4)+1/2 (10)(4)²
=1/2 (160)
=80m
t=6
s= (0)(6)+1/2(10)(6)²
= 1/2 (360)
= 180
Ratio = 80 : 180
= 4 : 9
Hmm.. Got the same answer as well. Will asked teacher for the solution.
I can’t understand why da/dt is jerk though.
Wow, it looks simple but it is a tough question. Hey Chris, do the question stated that the friction and inertia are neglected? And is it moving horizontally? Cause it will make some different:)
Kok Kuan, this is form 4 and 5 physics level.
On the other hand, the question only provided the information I have typed out.
JY, da/dt = jerk. The rate of change of acceleration against time is called jerk.
oo..haha..pai sie man..then i have no idea to get the answer adi:)
Hmm…
I got 4:9 no matter how I do it.
Unless it’s y:x+y, or else I don’t know how to get a 9:13. =)
Maybe it was intended to be y : x+y and they made a mistake in the question.. haha~
Ladida, tell me when you’ve figured it out, k?
in fact, it’s better not to.
I got 4:9 ratio as well. But you don’t have to assume that a is anything
No need to think that much lah.
Asked my lecturer, he also agreed to the 4:9.
hi, andar here, i just read your post. i like very much. agree to you, sir.
Thanks for your comments =]