projectile motion problem with no initial velocity given

[jrm1508]

Homework Statement

A tennis ball is thrown from an elevation of 2m, at an angle of 40°. If the ball travels 250m
before it hits the ground, what velocity was it thrown at?

Relevant Equations

Kinematic equations.

I don't know how to solve projectile motion problems when there was no initial velocity given, also no final velocity, or time. Please help

 

[Philip Koeck]

Homework Statement: A tennis ball is thrown from an elevation of 2m, at an angle of 40°. If the ball travels 250m
before it hits the ground, what velocity was it thrown at?
Relevant Equations: Kinematic equations.

I don't know how to solve projectile motion problems when there was no initial velocity given, also no final velocity, or time. Please help

Start by writing down the equations for x and y. See where that takes you.

 

[Orodruin]

The homework rules of PF requires you to show at least some effort to find the solution yourself.

The problem is literally to find the initial velocity. I suggest you work symbolically to find expressions involving the quantities given in the problem and the initial velocity. Preferably starting from the relevant equations that you did not write. (Please write out the equations you think are relevant).

 

[PeroK]

Homework Statement: A tennis ball is thrown from an elevation of 2m, at an angle of 40°. If the ball travels 250m
before it hits the ground, what velocity was it thrown at?
Relevant Equations: Kinematic equations.

I don't know how to solve projectile motion problems when there was no initial velocity given, also no final velocity, or time. Please help

The initial speed is $u$ and the time of flight is $\Delta t$.

PS if you are really stuck with this, forget about the initial height above the ground and take the range to be $250m$. Can you find $u$ in that case?