[Kinematics] Calculating the maximum height reached by the ball

[Slimy0233]

Homework Statement

A ball is thrown up at a speed of 4.0 m/s. Find the
maximum height reached by the ball. Take $g = 10 m/s^2$

Relevant Equations

$v = u +at$
$S = ut +0.5(at^2)$

I realize I can solve the other way too. But I want to solve using the equations
$v = u +at$
$S = ut +0.5(at^2)$

and I don't know why I didn't get the right answer. Thank you for your help!

 

[kuruman]

You forgot the minus sign in front of the acceleration.

 

[Slimy0233]

You forgot the minus sign in front of the acceleration.

ahh.... my good old archnemesis: the minus sign.

Thank you for pointing that out!

 

[kuruman]

An additional check to this kind of problem is to calculate the position at twice the time to maximum height. It should be zero because what goes up must come down, as they say.

 

[Slimy0233]

An additional check to this kind of problem is to calculate the position at twice the time to maximum height. It should be zero because what goes up must come down, as they say.

Thank you That's helpful. I will do that from now on.