# Can I find time without knowing initial velocity?

Kearnsy101
1. My problem is I know displacement is 20m, acceleration is -5.4m/s, final velocity is 0m/s, coefficient of friction=0.55, the object slowing down weighs 1000kg, can I find initial velocity and the time it took to slow down and if so how? I have no idea how to go about this problem

2. Equations of motion and coeffcient of friction = frictional force/normal force?? maybe F=ma

3. As I said I really dunno how to start this one or if its even possible at my level.

## Answers and Replies

LawrenceC
Do you have a formula that relates final velocity to initial velocity plus an acceleration-distance term?

You can also do this problem with work-energy relationships if you've studied that.

Hint:

Take the usual equation: d=V0*t+.5*a*t^2 and eliminate the variable t by inserting the relationship between final velocity, acceleration, and time. Solve for final velocity.

Kearnsy101
I woke up this morning, looked at this and it all jsut clicked in my head thankyou.

titaniumpen
Is the initial velocity 14.7 m/s^2?

LawrenceC
That's it.