Lab-3

Group 3: Andrew, Dan, Nick, Tim

Lab: Impulse of a softball Dan Rosenblatt Andrew Vlasak Tim McTiernan Nick Rossi Period 4 Date done: 2/5/10 Date due: 2/8/10


 * Objective**: What is the velocity of a softball?


 * Hypothesis**: The velocity of the softball is directly related to that of the entire system. The greater the force you use to toss the softball, the the velocity of the box will be greater, and will have moved further, giving it a bigger displacement.

Mass of softball (kg): .184 Mass of packed box (kg): 1.4 Total mass of packed box and softball (kg): 1.587


 * Data Table** of Softball Velocity


 * Velocity Time Graph** of Trials




 * Calculations**:

W= f x d W= 6 x .24 W= 1.44J

W=1.44 KE=W

KE=1/2mv^2 1.44=1/2(1.587)v^2 v^2=1.81 v=1.35 m/s

Impulse of ball alone

mass of ball(v2-v1) .184(v2-v1) -solve for v1 .184(v2-11.68) .184 + v2 = 11.68 v2= 63.5 m/s

mv=(m(ball)+m(box)V2 .184(V of ball)-(1.84+1.4)1.44 .184(V of ball) =2.28096 V of ball= 12.4 m/s

Mball/box*(Vball/box) 1.587*1.35=2.14

Discussion Questions:

1. What assumptions did you make in order to complete the calculations in this experiment? We assumed that the initial velocity was the largest velocity.

2. How else could you have calculated the initial velocity (without using energy or momentum conservation)? We could have used kinematics along with dynamics. We already had all that we needed to do kinematics. We had the mass, distance and final velocity. We also had friction force. We would use these in dynamics then find out the initial velocity using kinematics.

3. Why is the impulse-momentum relationship a useful one? It is useful because it proves Newton's Third Law. The law states that impulse and momentum have the same value.

4. Find the magnitude of the impulse delivered momentum. J = F*t J = (1000 N)(.05s) J = 50 N/S 5. Determine the change in the object's momentum. The change in momentum is equal to the answer in the previous question.

6. If the object's original velocity was -10m/sec, calculate its final velocity. 50 (Vf +10) = 50 Vf +10 = 1 Vf = -9 m/s

7. What was the magnitude of the "average force" acting on the object during the time graphed? (0.05)(1000) + (0.10)(1000) / 2 = 100N/S Conclusion:

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Our Percent error occurred between 1.94% and 15.84%. Sources of error could have been the force used to throw the softball. There is no way to replicate the exact same amount of force each time with a human. Another source of error could have been the distance the thrower stood from the box. A distance should be designated for the thrower to stand. A final source of error could have been the throwing motion used by the thrower. The thrower should have only used one of underhand or overhand instead of both. ======

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 When we said, " The velocity of the softball is directly related to that of the entire system. The greater the force you use to toss the softball, the the velocity of the box will be greater, and will have moved further, giving it a bigger displacement.", this was true. By recording data we proved our hypothesis true. We could use this in real life if we would like to see how safe a car is going at a certain mph. To fix this lab I would have a pitching machine that has an exact speed and distance every single time you use it. This would fix most of the error. ======

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 In order to solve these errors, we must also set a specific distance and throwing style for the lab. The thrower should stand at a set distance such as 4 meters and should only throw underhand or overhand. ======

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 This lab can be related to many real life applications. One can be the act of shooting a bullet. Once you shoot a gun,I presents a force on the object that it is shot at, just like what happened with the softball hitting the box in our lab. Also, in baseball, the harder the pitcher throws, the more the catcher gets pushed back. This is because of the high velocity and momentum of the ball. ======