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Momentum, Impulse, Work, Power

Momentum, Impulse, Work, Power. Harmandip Singh, Nasif Mahmud, Mohammed Yeashin, and Ajla Dupljak. What is Momentum ?. Momentum  – a measurement of the tendency of an object to stay in motion. SI Unit: [kg-m/s] Formula: momentum = (mass)(velocity) or p = mv. Momentum continued.

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Momentum, Impulse, Work, Power

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  1. Momentum, Impulse, Work, Power Harmandip Singh, Nasif Mahmud, Mohammed Yeashin, and Ajla Dupljak

  2. What is Momentum? Momentum – a measurement of the tendency of an object to stay in motion. SI Unit: [kg-m/s] Formula: momentum = (mass)(velocity) or p = mv

  3. Momentum continued - The momentum of a body is proportional to both its mass and velocity. If either one increases the momentum will also increase. - Momentum is a vector quantity whose direction is the same as the object's velocity.

  4. Practice Problem 1 1. If the mass of an object is 5kg, and the velocity is 7m/s, what is the momentum?

  5. Answer Formula first : p = mv p = (5kg)(7 m/s) 35 kg-m/s

  6. Problem # 2 2. What is the value of the momentum of a 10 kg ball running down a bowling alley at a speed of 5 m/s?

  7. Answer Formula first: p = mv p = (10 kg)(5 m/s)  50 kg-m/s

  8. Impulse Impulse- the product of the net force acting on an object and the time during which the force acts. The symbol for impulse is J. SI Unit: [kg-m/s] or [Ns] (Equivalent to momentum)The unit for impulse and the unit for momentum are equivalent. The Impulse is also the change in momentum for an object in motion. 

  9. Calculating Impulse •J= F net(T) = ΔP •(Force)(Time) = Impulse [kg * m/s2] •Δp= mΔv –Δp= m(v’-v) –Δp= mv’-mv –Δp= p’-p

  10. Practice Problem 3 3. A gust of wind exerts a 300. N net force on a 1000.-kg sailboat for 15 s. What is the change in the momentum and velocity of the boat?

  11. Answer Formulas first : J =Ft, p=mv,J= Δp J= (300.N)(15 s)= 4500  J= Δp= 4500kg-m/s p=mv v=p/m= (4500kg-m/s)/(1000.kg)= 4.5m/s

  12. Demonstration http://www.youtube.com/watch?v=NBaFIiBGjpI HW: AMSCO pg. 36-37  #153, 162, 170

  13. Work Work: In physics, work is done whenever a force acts on an object in the direction of the objects motion. If an object is not in motion no work is being done. Si Unit: J (Joule)1J = 1newton · meter = 1N · m- Work is the product of the magnitude of the applied force F and the objects displacement d in the direction of the force.-When calculating force only the force parallel to the objects motion can be used.-Work is a scalar quantity. If an object is not moving no work is being done.

  14. Practicing with Work and Power 1. How much work is done on a downhill skier by an average braking force of 9.8 × 102 Newtons to stop her in a distance of 10. meters?

  15. Solutions    1. Formula first: W=Fd     W= 9.8 × 102 N·10.m W=  9.8 ×103J

  16. 2. What is the work required to raise a 10. - kilogram box from the surface of the earth to a height of 5.0 meters?

  17. 2. Formulas first: w=mg, W=Fd     w= 10.kg × 9.8 m/s2     w= 98. N     W=Fd     W= 98.N ×5.0m     W= 490J

  18. Power Power is the amount of work done per unit time. Like work, it is a scalar quantity. The symbol for power is P. Power = (work/time) • P=W/t  • Since W=Fd, we can write: P= (Fd/t). • Since v= d/t we can write: P= (Fd/t)=Fv. • Thus, power can also be expressed as the product of the applied force and the velocity of the object • SI Unit = Watts --> J/Sec 

  19. 3. If energy is supplied at the rate of 10 watts, how much work is done during 2 seconds?

  20. 3. Formula first: P=W/t     Pt=W     10watts × 2s= W 20J=W

  21. Work and Power Demonstration     HW: AMSCO pg. 59-60  #1, 9, 17

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