Lab-5

Impulse of Softball Carly Youssouf, Jennifer Muller, Erika Silverman, Ashley Karkenny period 4 2/2/10 - 2/8/1

Mass of Softball: 0.185 kg Mass of Packed Box: 1.2 kg Mass of Packed Box and Softball: 1.385 kg



Purpose/Objective What is velocity of softball?

Hypothesis with Rationale The softball's initial velocity will be close to or the same as the velocity of the softball and the box, because the force of the ball on the box and the box on the ball are equal, which makes the impulses and momentum of the box and ball equal.

Sample Calculations Work = friction force • distance • cosφ = (5)(.152) (1) = .76 J

Kinetic Energy = Work = friction force • distance • cosφ = (5)(.152) (1) = .76 J

Velocity of box-ball (v2) KE = ½ mv2 .76 = ½ (1.385) v2 .76 = .639v2 √1.10 = √ v2 1.05 m/s= v2

Impulse of box-ball system = mv = 1.385 (1.05) = 1.45 kg•m/s

Impulse of ball only = Impulse of box ball = 1.45 kg•m/s

Initial Velocity of the ball = Impulse = mv1 1.45 = (.185) v1 7.84 = v1 % Difference = ⎟ actual – individual ⎟ / actual • 100 = ⎟ 7.84 - 7.45 ⎟ / 7.84 • 100 = 5%

Discussion Questions 1.) It was assumed that the fast part of the softball's path was when it was first released. We used that assumption, and looked at the max height on the graph as the initial velocity. 2.) We could have calculated initial velocity by using kinematics and dynamics. We can use the mass, friction, distance traveled, and final velocity to solve for acceleration and then continue to find our answer. 3.) According to Newton's third law, the change and momentum and impulse are equal. 4.) Magnitude of the impulse J=Ft J=1000*.05 J=50 N*s 5.) The change in momentum is equal to the magnitude of the impulse, 50 kg*m/s 6.) calculate the final velocity if the original was -10 m/s m(vf-vi)=impulse 50(vf+10)=50 vf+10=1 vf=-9 m/s 7.) magnitude of the average force .05*1000+.1*1000/2=100

Evaluation/Conclusion The purpose was satisfied because the hypothesis was proven correct. The velocity of the ball was similar to the velocity of the ball and the box because the impulse of the box equals the impulse of the ball. Our percent difference for each trial were relatively low, starting from 2.45% to 15.05%. Our data was accurate enough to give us good results, in order to prove our hypothesis. An error people could have had in their experiment is if the displacements were inconsistent with each other. If each time the thrower started in a different spot, their displacement would not be the same each time, causing there to be different initial velocities. Another error could be the data we were recording from data studio. We were recording the maximum height for our initial velocity, but if the thrower was not releasing the ball at maximum height, the data could be incorrect. Some ways to correct these errors are if the throwers are consistent with their positioning before throwing the ball so each displacement was similar. Also, if the thrower made sure they were releasing the ball at maximum height, they would have more accurate data.