What is the Peak Height of a Tennis Ball Shot Upward?

[Leo34005]

Homework Statement

A tennis ball is shot vertically upward in an evacuated chamber(neglect air resistance) with an initial speed of 20m/s at time t=0s.

How high does the ball rise?

A)98.0m
B)72.4m
C)20.4m
D)10.2m
E)40.8m


Approximately how long does it take the tennis ball to reach its maximum height?

A)4.08s
B)9.08s
C)0.50s
D)6.08s
E)2.04s

Homework Equations

The Attempt at a Solution

 

[kuruman]

What are your thoughts and your equations regarding this matter?

 

[Leo34005]

Its a freefall question regarding physics

 

[kuruman]

And what do you know about free fall questions regarding physics? What are the relevant equations?

 

[Leo34005]

Dont know anything. Would you mind?

 

[kuruman]

If you don't know anything but want to learn about this question, a good place to start is here

https://www.physicsforums.com/showthread.php?t=300756

 

[DrTravia]

Homework Statement

A tennis ball is shot vertically upward in an evacuated chamber(neglect air resistance) with an initial speed of 20m/s at time t=0s.

How high does the ball rise?

A)98.0m
B)72.4m
C)20.4m
D)10.2m
E)40.8m


Approximately how long does it take the tennis ball to reach its maximum height?

A)4.08s
B)9.08s
C)0.50s
D)6.08s
E)2.04s

Homework Equations

The Attempt at a Solution

I learn the reasoning behind the equations, this let's you forget the equations formal setup while still being able to work it out

initial speed/gravity = time it takes to reach the top
so in this particular one it would be

20 divided by 9.8 (constant acceleration caused by gravity)

That gives you your time

Take the time that you got and times it by the initial velocity and divide it by 2

(2.04 * 20) / 2

now this is a home-brew formula that i use to save some time when I don't need to be exact, itll be 0.1 off or somewhere around that area so if you need it to be exact then you need to do

(20*2.04)-(4.9*2.04²)

20 is the initial velocity as he throws it up

2.04 is the time it takes for it to reach the top

4.9 is half of 9.8, which is the acceleration caused by gravity

the formula is

ymax = Velocity_initial*Time - ¹/₂Acceleration*Time²

Hope this amatuer helped out a bit.

Rise = C
Time = E