- #1

- 5

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X=Xo+Vo+(1/2)at

^{2}

Car: X=95t

^{2}

Truck: X=75t

^{2}

Put both formulas equal to each other and solve for t. But where do I plug in the 100m that the car is behind? Thanks.

- Thread starter imagiro1
- Start date

- #1

- 5

- 0

X=Xo+Vo+(1/2)at

Car: X=95t

Truck: X=75t

Put both formulas equal to each other and solve for t. But where do I plug in the 100m that the car is behind? Thanks.

- #2

tiny-tim

Science Advisor

Homework Helper

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Hi imagiro1! Welcome to PF!

Nooo …X=Xo+Vo+(1/2)at^{2}

Car: X=95t^{2}

Truck: X=75t^{2}

i] it's X=Xo+Vot+(1/2)at

ii] a (the acceleration) is obviously zero, isn't it?

iii] that would be the Xo (a different one for each vehicle, of course)Put both formulas equal to each other and solve for t. But where do I plug in the 100m that the car is behind? Thanks.

- #3

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I ended up with Xc=.110+95t and Xt=75t, which gave me the right answer, but negative. I tried it again with Xc=95t and Xt=.110-75t and it gave me the 20 sec which is the answer.

If I change it to -.110 would that be the same thing as saying the car is .110km behind the truck?

- #4

tiny-tim

Science Advisor

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The car is 100m behind the truck …I ended up with Xc=.110+95t and Xt=75t, which gave me the right answer, but negative. …

so if the truck is at position 0 at time 0 (consistent with X

- #5

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-.110+95t. Awesome. Thanks for the help. I'm sure I'll be back later.

- #6

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Then, once you regard space and time as variables in a "calculus" way, you'll have no problem in solving problems like this and a lot more complicated that you never expected, even trying, before.

That's my advice, HOPE it's usefull.

Good night and good science

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