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Understanding Work, Energy, and Momentum: Principles and Applications in Physics

This educational resource covers the essentials of work, energy, and momentum, guiding students through key concepts such as the work-energy theorem, kinetic and potential energy, and conservation laws. Students will learn to calculate mechanical energy, power, and momentum in various scenarios. The resource also explains the relationship between work and energy transformations, applying principles like impulse and conservation in one-dimensional systems. Ideal for learners aiming to grasp foundational physics concepts and enhance their problem-solving skills.

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Understanding Work, Energy, and Momentum: Principles and Applications in Physics

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Presentation Transcript

  1. Work/Energy

  2. The student will… • Investigate and calculate quantities using the work-energy theorem in various situations • Investigate examples of kinetic and potential energy and their transformations • Calculate the mechanical energy of, power generated within, impulse applied to, and momentum of a physical system • Demonstrate and apply the laws of conservation of energy and conservation of momentum in one dimension

  3. Work W = Fd W – work (J) F – Force (N) d – distance/displacement (m) For work to be done, the object must move Displacement (distance) and force must be parallel for work to be done, NOT perpendicular

  4. Potential Energy (PE) • Stored energy • Gravitational (PEg) PEg = mgh • Elastic (PEe) PEe = ½kx² mass Gravity (-9.8) Height (neg) Distance stretched or compressed Spring constant

  5. Kinetic Energy (KE) • Energy of moving objects KE = ½ mv² mass velocity

  6. Conservation of Energy • Energy can’t be created or destroyed • Mechanical Energy (total energy) stays the same ME = KE + PE ME = ½ mv² + mgh

  7. Total energy at any point must remain the same, so: KEi + PEi = KEf + PEf ½ mvi² + mghi = ½ mvf² + mghf

  8. Work-Energy Theorem • Work done is equal to the change in the kinetic energy of an object W = ∆KE W = KEf – KEi W = ½ mvf² - ½ mvi²

  9. Power • Power is the rate at which work is done • The faster you get work done, the more powerful you are • Power is measured in Watts P = W / t P = Fd / t P = (ma)d / t

  10. Momentum • Symbol is p • Measured in kg·m/s p = mv velocity momentum mass

  11. Conservation of Momentum • Total momentum before and after two objects collide is conserved, so momentum before = momentum after m1v1i + m2v2i = m1v1f + m2v2f Object 1 mass Object 2 Final velocity Object 2 mass Object 1 mass Object 2 mass Object 1 Initial velocity Object 2 initial velocity Object 1 Final velocity

  12. Impulse The force applied over time, or the change in momentum of an object Symbol is J J = F ∆t = m∆v Impulse Change in velocity (vf – vi) Mass Force Change In time

  13. Which of the following is the best example of kinetic energy being transformed into potential energy? A

  14. If a powerlifter raises a 500 N weight a distance of 2.0 meters in 0.5 seconds, what is his power output in watts? A

  15. A 15.00 kg crate is accelerated from 3.000 m/s to 8.000 m/s. What is the amount of work needed to accelerate the crate? a. 147 J b. 412.5 J c. 67.5 J d. 480 J B

  16. If you double the mass of a moving object and the velocity stays constant, how is the momentum of the object affected? a. p b. 4p c. 2p d. ½ p C

  17. What is the momentum of .03 kg bullet traveling at 250 m/s? 95.7 kgm/s b. 937.5 kgm/s c. 8333 kgm/s d. 7.5 kgm/s D

  18. A force does work on an object if a component of the force B

  19. The more powerful the motor is, B

  20. A 3.00 kg toy falls from a height of 10.0 m. Just before hitting the ground, what will be its kinetic energy? (Disregard air resistance. g=9.81m/s2.) D

  21. What is the kinetic energy of a 0.135 kg baseball thrown at 40.0 m/s? C

  22. Which of the following energy forms is associated with an object in motion? D

  23. A 1000 kg truck moving at 10 m/s runs into a concrete wall. It takes 1.0 second for the truck to completely stop. What is the magnitude of force exerted on the truck during the collision? D

  24. A crane lifts two 100 kg loads of building materials to the top of a building under construction. The first load is lifted in 10 s and the second load is lifted in 13 s. Which of the following statements best compares the work and power used by the crane lifting the two loads? C

  25. The diagram below shows the path of a student on a roller coaster starting from rest at point W. The student rides in a frictionless cart past point Z, whichis at ground level. Which of the following statements best describes the energy of the student and the cart from point W to point Z? H

  26. A force of 500 N is exerted on a baseball by the bat for .001 s. What is the change in momentum of the baseball? A

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