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Determine the time it take for the car and the truck to meet

  • Thread starter Arden
  • Start date
5
0
a car starts from rest at a point 300m from a truch that is moving at a constant rate of 30m/s toward the car. IF the car accelerates at .8m/s2, determine the time it take for the car and the truck to meet.
s=300
This is what I did
Car:
Vi = 0, a = .8
Vf^2=2as = Vf=21.9

Vf=at
21.9/.8 = 27.38
t=27.38sec

Truck:
S=(V/2)t
S=(15)t
300/15 = 20
t=20

They meet after (27.38 -20) = 7.38 seconds.

The answer given is 8.94seconds. Not sure what I am doing wrong?????
 

James R

Science Advisor
Homework Helper
Gold Member
600
15
You assumed the truck meets the car at 300 m. It doesn't, because the truck is moving towards the car.
 

Pyrrhus

Homework Helper
2,160
1
You will need to set up your equation such as the car will cover a distance x, which will be the distance the truck meets the car, but the truck will cover a distance x+300.
 
208
0
dont you mean 300 - x
 

Pyrrhus

Homework Helper
2,160
1
Depends on where you put your coordinate system, i put the origin on the car.
 
5
0
Thank you all for your help - Arden
 

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