# Long Jump Question

## Homework Statement

A runner jumps at 30 degrees to the ground and covers 8.90 m. What was the takeoff speed?

## The Attempt at a Solution

I have no idea where to start...

rl.bhat
Homework Helper
Resolve the velocity in to vertical and horizontal components.
What happens to these components with respect to time?

how would i go about solving the velocity for each component?

rl.bhat
Homework Helper
If v is the velocity what are the vertical and horizontal components?

honestly, i have no idea

rl.bhat
Homework Helper
Open any text book. And refer the motion in two dimension.

but all i have is the angle of the jump and the distance...no time or anything

rl.bhat
Homework Helper
Using proper equation you can find the remaining unknown quantities. Try to find out the equations.

do u mean these formulas?

Fx = cos A * F1
Fy = sin A * F1

honestly, im struggling and have no idea what to do...

rl.bhat
Homework Helper
do u mean these formulas?

Fx = cos A * F1
Fy = sin A * F1
Yes. These are the two components. Only replace F by v for the velocity.
In that x component remains constant, because there is no acceleration in that direction. If t is the time of flight, then x = vcosθ*t.
In the vertical direction, the initial velocity is vsinθ. What is the final velocity when it reaches the maximum height. And what is the time taken to reach the maximum height?

when u say x = vcosθ*t , what is v? the speed before the jump?

Last edited:
rl.bhat
Homework Helper
No. You have to find out. I have told you to write down all the kinematic equations. Then I will tell you which equation to be used to find the time.

oh wouldnt the final velocity be 0 when it reaches a maximum height? because he would have stopped moving up?

rl.bhat
Homework Helper
Yes.

I dont know how to find the time it would take to reach the max height.

Last edited:
rl.bhat
Homework Helper
Why can't you write down all the relevant kinematic equation. In the post submitted to PF, this is the second requirement.. You have not submitted that. Do it first now.