Inertia. problem solved
SOrry if Im in wrong section but I got problems with my physics homework here it it:
A car was moving at a constant velocity of 40 m s-1 .The driver saw an obstacle in front and he immediately stepped o the brake pedal.He managed to stop the car in 8 s.The distance of the obstacle from the car when the driver spotted it was 180 m.How far was the obstacle from the car after it stopped?
Thanks for helping ,I tried my best but I just cant figured it.
Inertia. problem solved
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It's SUVAT.
s = ? What we want to find out.
u = 40 ms^-1
v = 0 ms^-1
a = X We don't know and probably don't need to know.
t = 8 s
To find the distance it takes for the car to stop, use s = t(u+v)/2).
So,
s = 8 * (40/2)
s = 8 * 20
s = 160 m
To find the distance the car stops from the obstacle, simply take the distance it takes to stop the car away from the distance the car was from the obstacle originally.
180 - 160 = 20
So the car stopped 20m away from the obstacle.
Last edited by Unknown; 02-24-2015 at 04:51 AM.
aweosmejules (02-24-2015),Mokou-Sama (02-24-2015)
Thanks for the help but what the differences between s=ut+1/2at2 and s = t(u+v)/2 that you given?
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Is it just the same but two different ways to get them?
Edit:I pretty understand that u=40ms^-1 because of constant velocity so the v=0ms^-1 because the car was stopped and the constant velocity too?
Last edited by aweosmejules; 02-24-2015 at 05:15 AM.
No problem.
To be able to use the formula;
s = ut + 1/2 * (at^2) ,
the acceleration of the car would need to be know. Obviously this could be calculated because acceleration is the change in velocity over time. So by using the formula;
a = (v - u) / t ,
we could find this out. So yeah that formula could be used easily but it does involve an additional calculation. Yeah it's just another way to do it.
You're told that the car is moving at a constant velocity of 40 ms^-1 and decelerates to a stop. This means that the car was originally moving at 40 ms^-1. Therefore this is the initial velocity, u. The car stops so you know that the final velocity has to be 0 ms^-1, so v = 0.
Last edited by Unknown; 02-24-2015 at 05:30 AM.
aweosmejules (02-24-2015)
Thx for the help +rep! @arunforce pls close this thread.
aweosmejules (02-24-2015)
Alevel physics haha, .... I remember this SUVAT!! :0
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Brilliant, I was gonna solve it but Unknown came first.
Formerly known as gamer4evere
That's some kindergarten physic shit right there. Answer is obviously 666m away.. Gawsh.