Velocity Ball In Air: 4s, 81.6m

Click For Summary

Homework Help Overview

The discussion revolves around a physics problem involving the motion of a ball thrown upwards with an initial velocity. Participants are exploring the time the ball spends in the air and its final velocity upon returning to the ground.

Discussion Character

  • Exploratory, Assumption checking, Conceptual clarification

Approaches and Questions Raised

  • Participants discuss the initial conditions of the problem, including initial velocity and acceleration due to gravity. There is confusion regarding the total time the ball is in the air and the final velocity upon impact. Some participants question the interpretation of the final velocity and whether it should be zero when the ball hits the ground.

Discussion Status

The discussion is ongoing, with participants providing feedback on each other's calculations and interpretations. Some guidance has been offered regarding the correct understanding of final velocity and the implications of the equations used. There is a recognition of the need to clarify the distinction between the initial velocity and the final velocity just before impact.

Contextual Notes

Participants are working under the constraints of a homework problem, which may limit the information available for discussion. There is an emphasis on understanding the motion of the ball throughout its trajectory, including both ascent and descent.

C42711
Messages
22
Reaction score
0
A ball is thrown with an initial upwards velocity of 40.0 m/s.
a)How long is it in the air?
b)How fast is it going when it hits the ground?

I decided my given was:
vi= 40.0 m/s
vf=0 m/s
a= -9.8 m/s2

I solved for time and distance using the big four and for
a)4s
b)81.6m

Is this correct?
 
Physics news on Phys.org
C42711 said:
A ball is thrown with an initial upwards velocity of 40.0 m/s.
a)How long is it in the air?
b)How fast is it going when it hits the ground?

I decided my given was:
vi= 40.0 m/s
vf=0 m/s
a= -9.8 m/s2

I solved for time and distance using the big four and for
a)4s
b)81.6m

Is this correct?

Not really. You have calculated how long it takes to stop traveling up, and how high it gets.
The questions were how long is it in the air; it has to come down again, and how fast it is traveling when it gets back down.
 
Okay, how is this?
a) 8 s

And then for b, I'm not sure what I'm looking for to be how fast. I would have thought velocity, but they gave me velocity, so that's not it. And it can't be acceleration because that's gravity. So I am confused on what I'm looking for.
 
C42711 said:
Okay, how is this?
a) 8 s

And then for b, I'm not sure what I'm looking for to be how fast. I would have thought velocity, but they gave me velocity, so that's not it. And it can't be acceleration because that's gravity. So I am confused on what I'm looking for.

OK, you said they gave you the velocity. what was it then? remember you want the velocity just before it hits the ground, not the velocity at which it was thown.
 
C42711 said:
A ball is thrown with an initial upwards velocity of 40.0 m/s.
a)How long is it in the air?
b)How fast is it going when it hits the ground?

I decided my given was:
vi= 40.0 m/s
vf=0 m/s
a= -9.8 m/s2

I solved for time and distance using the big four and for
a)4s
b)81.6m

Is this correct?

Just realized you may have said vf=0 m/s since when the ball hits the ground it will stop.
The question is really asking you at what speed the ball is traveling as it reaches the ground.
 
So I am looking for final velocity and it's not zero?
If so, I got it to be .61 m/s, but that seems awfully low, so I don't know. I used this equation:
vf= vi2+2*a*d
 
C42711 said:
So I am looking for final velocity and it's not zero?
If so, I got it to be .61 m/s, but that seems awfully low, so I don't know. I used this equation:
vf= vi2+2*a*d

I trust you actually used

vf2= vi2+2*a*d

What value for d did you use?

I hope it was zero. [notice what happens to that formula when d = 0]

Hint:

put something in your hand, a coin, a pen, a ball.

Now toss it up as if you were juggling a single object - ie repeatedly.

While you are doing that, watch how fast the object leaves your hand, then how fast it arrives back at your hand.
 

Similar threads

Potential and Kinetic energy equations including drag coefficient
  • · Replies 1 ·
Replies
1
Views
1K
Question about Projectile Motion: Throwing a Flower Pot from a Balcony
  • · Replies 18 ·
Replies
18
Views
2K
Conservation of momentum (wrecking ball hits a stationary object)
  • · Replies 10 ·
Replies
10
Views
3K
Oblique soccer shot calculation task
  • · Replies 38 ·
2
Replies
38
Views
4K
Why is my time calculation for the ball's flight incorrect?
  • · Replies 15 ·
Replies
15
Views
5K
Relative velocity passing a ball between two soccer players
  • · Replies 5 ·
Replies
5
Views
3K
Solve Kinematics Q13: Golf Ball Height & Distance
  • · Replies 6 ·
Replies
6
Views
2K
Why do I keep getting friction coefficient as a negative?
  • · Replies 17 ·
Replies
17
Views
3K
Projectile Motion Problem: Kicking a soccer ball over a fence
  • · Replies 11 ·
Replies
11
Views
3K
How do i account for the height for projectile motion
  • · Replies 7 ·
Replies
7
Views
3K