Physics Honors Impulse and Momentum Study Guide Preview
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Physics Honors Impulse and Momentum Study Guide Thank you for purchasing the Physics Honors Study Guide made by Easy-Notes! The purpose of this study guide is to incorporate the experience of previous and current Physics students to facilitate the learning of Physics for high school students. This study guide will provide detailed explanations for concepts in these chapters, and will also explain in detail example problems in the text book. This study guide is for educational purposes only. Any dissemination or alteration of this document without the written consent of Easy-Notes is subject to legal terms. Momentum: 1. An object’s linear momentum equals the product of its mass and its velocity. 2. The units for momentum are kilogram∙meters/second (kg∙m/s). 3. Momentum is a vector quantity. The momentum vector points in the same direction as the velocity vector. If a 0.14 kg truck is moving to the right and has a velocity of 1.2 m/s, then its momentum is: p = momentum m = mass v = velocity p = mv p = 0.14 kg x 1.2 m/s = 0.17 kg•m/s to the right Relationship between momentum and Newton’s second law: ΣF = ∆P/∆T ΣF = net force ∆P = momentum ∆T = change in time The change in momentum is called the impulse of the force, and is represented by J. Impulse is a vector, has the same units as momentum, and points in the same direction as the change in momentum and as the force: J = F∆T = ∆P J = impulse (7 pages have been omitted in this preview) Force vs. Time diagram: Given the graph above, the force vs. time diagram is shown for a baseball hit by a bat from the moment of contact to the moment of the baseball leaving the bat. At the moment of contact, the bat and ball are moving toward each other. The force on the ball increases as they come together and the ball compresses against the bat. The force then decreases as the ball and the bat lose contact, and the force is zero again as the ball leaves the bat. Given that: Impulse = change in momentum = average force x elapsed time We can calculate the impulse by calculating the area under the curve (similar to calculating displacement by using the area of the velocity vs. time graph); we can do this because the units for such a calculation are N•S, which is the unit for impulse (change in momentum) according to the formula: ΣF = ∆P/∆T, Which implies that ∆P = ΣF x ∆T You can also calculate the momentum using the area under the rectangle shown in the graph. The length of the rectangle is the elapsed time, and the width is the average force exerted on the baseball. This calculation is valid according to this formula: J = F∆T = ∆P Given the above formulas, if a 0.14 kg baseball arrives at 40 m/s and leaves at 49 m/s in the opposite direction, and the contact time is 5.0 x 10-4 s, the average force exerted on the ball is: ΣF = ∆P/∆T
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