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 kg sailboat for 15 s. What is the change in the momentum and velocity of the boat?

11. Formulas first : J =Ft, p=mv,J= Δp J= (300.N)(15 s)= 4500
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 HW: AMSCO pg. 36-37 #153, 162, 170
HW: AMSCO pg  #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 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  #1, 9, 17