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Mechanics Question

A car accelerates uniformly from rest along a level road.The effects of air resistance on the car are negligible.The car travels 12 m in the second second of its journey.How far does it travel in the fourth second

How do you work this out?
Original post by Acrux
A car accelerates uniformly from rest along a level road.The effects of air resistance on the car are negligible.The car travels 12 m in the second second of its journey.How far does it travel in the fourth second

How do you work this out?


The car is accelerating uniformly, so try drawing a acceleration time graph for this question if u aint comfy with Suvat
Reply 2
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Zacken
22
Original post by Acrux
A car accelerates uniformly from rest along a level road.The effects of air resistance on the car are negligible.The car travels 12 m in the second second of its journey.How far does it travel in the fourth second

How do you work this out?


Set up your SUVAT equations, one in the second second and the second in the fourth second.
Reply 3
Avatar for Acrux
Acrux
OP
7
Original post by Zacken
Set up your SUVAT equations, one in the second second and the second in the fourth second.


What I am trying to work out with the SUVAT equations
Reply 4
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Zacken
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Original post by Acrux
What I am trying to work out with the SUVAT equations


You're gonna wanna find "s" in the forth second equation.
Original post by Acrux
A car accelerates uniformly from rest along a level road.The effects of air resistance on the car are negligible.The car travels 12 m in the second second of its journey.How far does it travel in the fourth second

How do you work this out?


The second second is from t=1 to t=2.

How far did it go from the start to t=1? We don't know, so call it s.
Then from the start to t=2 it went s+12.

Now set up two equations, eliminate s, and find a.

Edit: Too slow.

See if you can work out the fourth second now.
(edited 8 years ago)
Reply 6
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Acrux
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Original post by ghostwalker
The second second is from t=1 to t=2.

How far did it go from the start to t=1? We don't know, so call it s.
Then from the start to t=2 it went s+12.

Now set up two equations, eliminate s, and find a.

Edit: Too slow.

See if you can work out the fourth second now.

So One equation is s=ut+1/2at^2 the other s+12=ut+1/2at^2
Original post by Acrux
So One equation is s=ut+1/2at^2 the other s+12=ut+1/2at^2


It's along the right lines, but:
I'd put in all the values you know in each equation first, because as it stands the t in the first is not the same as the t in the second. Sort one equation at a time.

You know what u is.
You know what t in the first one is.
And you know what t in the second one is.
Reply 8
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Acrux
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Original post by ghostwalker
It's along the right lines, but:
I'd put in all the values you know in each equation first, because as it stands the t in the first is not the same as the t in the second. Sort one equation at a time.

You know what u is.
You know what t in the first one is.
And you know what t in the second one is.


Okay so Acceleration is 8ms^-2 and to the fourth second is 64m
Original post by Acrux
Okay so Acceleration is 8ms^-2 and to the fourth second is 64m


OK, that's how far it went from t=0 to t=4, but you want how far it went in the fourth second.
Reply 10
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Acrux
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Original post by ghostwalker
OK, that's how far it went from t=0 to t=4, but you want how far it went in the fourth second.


Okay i got the answer 28m
Original post by Acrux
Okay i got the answer 28m


:cool:

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