Calculating Final Velocity of Falling Balls

In summary, the conversation is about a student struggling with a physics concept and seeking help from others. The student has performed an experiment in lab and needs to calculate final velocities for different sized balls. There is confusion about the formulas and units to use, but it is eventually clarified that the correct formula is Vf = Vi + gt. The student also seeks advice on how to calculate horizontal velocity. The conversation ends with the student thanking everyone for their help and revealing the name of their high school.
  • #1
Crackle
2
0
Ok guys.

I've just come back from Thanksgiving holidays and I just can't seem to grasp this concept.

I have an X, Y, and t from the experiment that we did in lab today. I have a Vy of 91.2cm. I now need to calculate a VyFinal ( Vyf ). From what I have gathered the equation should come out to :

Vyf = Vy + g * t

So, in that said, my equations for the four balls ( diferent sizes ) should come out to be :

Vyf = 91.2cm + ( -9.80m/s2 * .50s ) ( my time for the ball to drop from 91.2cm high )

This would leave me adding a (cm) and a (m/s). That doesn't seem right to me because the units are odd.

I dropped each ball ( tennis, golf, nerf, and bouncy ) three times and recorded the time as t, the distance from which the ball traveled away from the dropping point as X, and Y being my constant at 91.2cm high off the ground. ( I believe this is going to become negative because the ball is traveling downward )

I have to do calculations for Vyf and Vx.

If X = (Vx)(t), then Vx = X/t correct? If this is true then my Vx would then be the distance from the counter to where the ball dropped divided by the amount of time it took to hit the ground.

I think I am on the right direction, I just need some advice to get me going.

Thanks Everyone,
Crackle
 
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  • #2
I believe the formula you want to use would be:

H = Vf*t - 1/2*a*t^2

H = the height that the balls fell...AKA 92.4 cm.
Vf = the final velocity of the balls, right before impact (what you're solving for)
t = the time it took to fall
a = the acceleration due to gravity, which is approximately equal to 9.81 m/s^2

Sub all of that in and you should be able to solve for the final velocity before impact.
 
  • #3
Yes, On your first part of the question, adding cm's to m/s would be incrroect. The correct formula is

final velocity = initial velocity + gt

since the ball is at rest when you drop it, the initial velocity would be 0 m/s.

Your 91.2 cm would be the initial height, not initial velocity. Earlier, you were incorrectly placing the 91.2 cm in as an initial velocity, which it isn't.

The horizontal velocity would be the horizontal distance traveled/ time. For this part of the lab, you would be on the right track.
 
  • #4
Actually, it would be much easier just to go

Vf = Vi + gt which is really just

final velocity = g * time
since Vi would be 0, as the object starts out at rest. Remember that g = -9.8 m/s^2
 
  • #5
..hey Crackle, i was just wondering, what's the name of the high school you go to. I remember actually doing that same lab last year in my physics class.
 
  • #6
Originally posted by thermodynamicaldude
..hey Crackle, i was just wondering, what's the name of the high school you go to. I remember actually doing that same lab last year in my physics class.

St. Charles Catholic

And thanks to everyone who helped me as well.

Lata,
Crackle
 

1. How does gravity affect the motion of falling balls?

Gravity is a force of attraction between any two objects with mass. When an object, such as a ball, falls towards the ground, it is being pulled by the Earth's gravitational force. This force causes the ball to accelerate towards the ground until it reaches its terminal velocity, which is the maximum speed it can reach during free fall.

2. What factors can affect the speed at which a ball falls due to gravity?

The speed at which a ball falls due to gravity is affected by several factors, including its mass, the air resistance it experiences, and the strength of the gravitational force. Objects with larger masses will experience a greater gravitational force and thus fall faster. Air resistance, or drag, can also slow down the ball's fall as it pushes against the object in the opposite direction of gravity.

3. Can gravity make a ball fall upwards?

No, gravity always pulls objects towards the center of mass of another object. In the case of a ball falling towards the ground, the Earth's center of mass is at its core. Therefore, the ball will always fall downwards towards the Earth's center.

4. How does the height from which a ball is dropped affect its falling speed?

The height from which a ball is dropped does not affect its falling speed due to gravity. Objects in free fall will always accelerate at the same rate, regardless of their initial height. However, the higher the starting point of the ball, the longer it will take to reach the ground due to the increased distance it needs to cover.

5. What is the relationship between mass and gravity in the context of falling balls?

The relationship between mass and gravity is described by Newton's Law of Universal Gravitation. It states that the strength of the gravitational force between two objects is directly proportional to their masses and inversely proportional to the square of the distance between them. This means that the greater the mass of the falling ball, the stronger the gravitational force pulling it towards the Earth.

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