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Throwing ball out of a moving car

  • #1

Homework Statement


A car is moving at 25m/s. A passenger, 1.5 m from the ground, can throw a ball at a max speed of 15 m/s and throws the ball out the window as he passes a bystander on the sidewalk. How fast is the ball moving when it leaves the passenger's hand and how far does the ball move relative to the bystander?


Homework Equations


For X component:
distance = velocity * time

For Y component:
x(f) = x(i) +v(i) + .5at2


The Attempt at a Solution


I believe that, relative to the bystander, the ball is moving at 40m/s. You can figure out the amount of time it takes the ball to reach the ground by solving for t for the Y component equation.
x(i) and v(i) = 0
a = g = 9.8m/s2
x(f) = 1.5m
solve, t = 0.55s

Now you just solve for the x component:
v = 40m/s
t = 0.55s
X = 22m

Is this correct? Thanks for the help.
 

Answers and Replies

  • #2
PhanthomJay
Science Advisor
Homework Helper
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Looks good!:approve: (assuming he throws the ball in the same direction as the car's movement)
 
  • #3
3
0
It seems you are answering for how far the ball moves before it hits the ground, but the question asks how far it has moved in relation to the pedestrian at the point of release. Wouldn't that make the distance the ball travels in relation to the pedestrian 0?
 
  • #4
7
0
The pedestrian is basically a fixed point. How would a moving object move zero distance in relation to a motionless one?
 
  • #5
3
0
The pedestrian is basically a fixed point. How would a moving object move zero distance in relation to a motionless one?

Extremely close to zero, in relation to the pedestrian, in that instant. I am probably wrong, that's why I'm asking.
 
  • #6
Extremely close to zero, in relation to the pedestrian, in that instant. I am probably wrong, that's why I'm asking.
Do you have a formula/any numbers to explain why you're thinking this way?
 
  • #7
3
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Do you have a formula/any numbers to explain why you're thinking this way?
Not at all, I'm hoping someone will pwn me with numbers so I can learn something here. It just seems logical that, in a snapshot in time, the ball hasn't moved in relation to the person, but I know logic is not the best thing to go on in these situations.

d = v * t, t = 0, or something extremely close to it, as the ball has not started it's journey yet (in relation to the pedestrian) as it has just arrived at it's starting point.
 
  • #8
Not at all, I'm hoping someone will pwn me with numbers so I can learn something here. It just seems logical that, in a snapshot in time, the ball hasn't moved in relation to the person, but I know logic is not the best thing to go on in these situations.

d = v * t, t = 0, or something extremely close to it, as the ball has not started it's journey yet (in relation to the pedestrian) as it has just arrived at it's starting point.
Hm, you may be getting confused, thinking the question is asking "in the moment the passenger releases the ball, how far has it moved relative to the bystander."

If the question was worded something along the lines of "...how far has the ball moved relative to the bystander when it hits the ground" does that make it clearer?
 
  • #9
3
0
If the question was worded something along the lines of "...how far has the ball moved relative to the bystander when it hits the ground" does that make it clearer?
Hah well yea of course, I said that in my post, but the question is not written that way.

"How fast is the ball moving when it leaves the passenger's hand and how far does the ball move relative to the bystander?"

The and implies that 'leaving the passengers hand' and 'ball move relative to the bystander' are recorded at the same instant.

I understand the question is not actually asking this (I assume at least), but if it where asking the question that I am, am I correct? That's all I'm wondering.
 
  • #10
Hah well yea of course, I said that in my post, but the question is not written that way.

"How fast is the ball moving when it leaves the passenger's hand and how far does the ball move relative to the bystander?"

The and implies that 'leaving the passengers hand' and 'ball move relative to the bystander' are recorded at the same instant.

I understand the question is not actually asking this (I assume at least), but if it where asking the question that I am, am I correct? That's all I'm wondering.
Oh, well yea. Haha.
 
  • #11
3
0
K, sweet, beers all around than. :smile:
 

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