No prefix: How far does a car move before running out of gas on a road?

[ArcherofScience]

car moving down road...

Homework Statement

A car is moving down a road at 45 km/hr when it runs out of gas. How far does the car move if it takes 6.0s to roll to a stop?

Homework Equations

x=(vi+vf)/2 *t I tried this equation, but I got the answer of 135 m. It says the answer is 37.5 m in the answers given by the teacher.

The Attempt at a Solution

I set it up this way:

vi: 45 km/hr
vf: 0
t= 6.0 s
x=?
x= (45+0)/2 * 6.0 = 135 mI want to know what I'm doing wrong, am I using the wrong equation? Thanks.

 

[SammyS]

Homework Statement

A car is moving down a road at 45 km/hr when it runs out of gas. How far does the car move if it takes 6.0s to roll to a stop?

Homework Equations

x=(vi+vf)/2 *t I tried this equation, but I got the answer of 135 m. It says the answer is 37.5 m in the answers given by the teacher.

The Attempt at a Solution

I set it up this way:

vi: 45 km/hr
vf: 0
t= 6.0 s
x=?
x= (45+0)/2 * 6.0 = 135 m

I want to know what I'm doing wrong, am I using the wrong equation? Thanks.

I suspect that you need to convert the velocity to m/sec.

 

[ArcherofScience]

yeh it worked, i got the right answer ! :D

thankyou! :)