How High and How Long Will the Apple Travel?

[lakhani7]

Homework Statement

maria throws an apple vertically upward from a height of 1.3 meters with an initial velocity of 2.4 m/s.
A) will the apple reach a friend in a treehouse 5.3 m above ground
B)how long will the apple be in the air before it hits the the ground

Homework Equations

vf^2=Vi^2+2ay

The Attempt at a Solution

A) i was able to get the answer for number one using the equation above.
0^2=2.4^2+2(-9.81*y)
-5.76=-19.62y
.3m=Y
B)i am not able to get the time however. i used vf=vi+at and i was unable to get the time.
0=2.4+9.81t
.244
the answer is .82 seconds.
if anyone can recommend me an equation to use i will be grateful.

 

[HallsofIvy]

Try y= (1/2)at^2+ vi t.

 

[LowlyPion]

Welcome to PF.

Here are some equations that might be useful.
https://www.physicsforums.com/showpost.php?p=905663&postcount=2

There are several ways to figure the answer to part b).

You can use the equation that relates y, Vy, and t and solve the quadratic for t.

You can also figure the time and height to get to maximum and then figure the time to fall.

V = a*t the first step is easy and you already have the height from part a).

Then all you have to do is figure the time to fall from that height and add in the first part.

 

[lakhani7]

nope that doesn't seem to help. i used the quadratic equation with it but to no avail

 

[LowlyPion]

Your .244 secs is really just the time to the max height. You still have to add in the downward time to fall.

x = 1.3 + .3 = 1.6 = 1/2g*t²

 

[lakhani7]

thanks lowly pion will try