Calculate Initial Speed of Ball Thrown Vertically 14m in 3s

In summary, the problem involves a ball being thrown vertically from ground level and caught 3.0 seconds later by a person on a balcony 14 meters above the ground. The goal is to determine the initial speed of the ball. The equation d = Vi.t + 1/2 a.t^2 can be used, with the acceleration due to gravity (a = -9.78 m/s^2) being the appropriate value to use. Using proper sign conventions for 'up' and 'down', the correct initial speed can be calculated.
  • #1
patelneel1994
26
0

Homework Statement


A ball thrown vertically from ground level is caught 3.0 s later by a person on a balcony which is 14 m above the ground. Determine the initial speed of the ball.

t = 3.0 s, d = 14 m, Vi = ?

Homework Equations


d = Vi.t + 1/2 a.t^2


The Attempt at a Solution


I have no idea how to get this problem. I don't know if the equation is right or not?


Thank You
 
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  • #2
You can certainly use that equation. What would you use for the acceleration? (Careful with signs.)
 
  • #3
How do I find acceleration?
 
  • #4
patelneel1994 said:
How do I find acceleration?
It's a projectile. You should know the acceleration.
 
  • #5
Is it 3 ms-2?
 
  • #6
patelneel1994 said:
Is it 3 ms-2?
No. Where in the world did that come from?
 
  • #7
I coudn't think of any. I thought time and acceleration some how are related, which are not.
Could we use gravity, which is 9.79 m/s2?
 
  • #8
patelneel1994 said:
I thought time and acceleration some how are related, which are not.
The acceleration is constant.

Could we use gravity, which is 9.79 m/s2?
Of course you should use the acceleration due to gravity!
 
  • #9
So if we solve using acceleration, then a = 0 right!
How can I solve using gravity? Is there any different formula?

Thank you
 
  • #10
patelneel1994 said:
So if we solve using acceleration, then a = 0 right!
No. Why would you think that?

How can I solve using gravity? Is there any different formula?
You have the right formula. For the acceleration, use the acceleration due to gravity.
 
  • #11
Sorry a = 9.78 m/s^2
I've tried that didn't ge the right answer.
14 = Vi . 3 s + [4.9 m/s^2 . 9 s^2]
14 - 44.1 / 3 s = Vi
 
  • #12
patelneel1994 said:
Sorry a = 9.78 m/s^2
What's the sign of the acceleration? Which way does gravity act?
 
  • #13
Gravity pull an object down towards the ground. a = 9.78 ms-2!
 
  • #14
patelneel1994 said:
Gravity pull an object down towards the ground. a = 9.78 ms-2!
Use a proper sign convention in your equation. Let 'up' be positive and 'down' be negative.
 
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  • #15
Tha gives me the right answer. So whenever its down - and up +
a = -9.78 ms-2
Thank you
 

Related to Calculate Initial Speed of Ball Thrown Vertically 14m in 3s

What is the formula for calculating initial speed of a ball thrown vertically?

The formula is v0 = gt, where v0 is the initial speed, g is the gravitational acceleration (9.8 m/s2 on Earth), and t is the time in seconds.

How do you calculate the gravitational acceleration (g)?

The gravitational acceleration can be calculated using the formula g = 2h/t2, where h is the height of the object and t is the time it takes to reach that height.

What is the unit of measurement for initial speed?

The unit of measurement for initial speed is meters per second (m/s).

Can the initial speed of a ball thrown vertically be negative?

Yes, the initial speed can be negative if the ball is thrown downwards, towards the ground.

What are the factors that can affect the initial speed of a ball thrown vertically?

The factors that can affect the initial speed of a ball thrown vertically are the height from which it is thrown, the angle at which it is thrown, air resistance, and the mass of the ball.

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