Summary

• Conservation of momentum
• Elastic & inelastic collisions
• Reverse collisions

• Class Quiz



• Reading Quiz



• Momentum & collisions
  • center of mass applet
  • two dimensions applet
  
  
• Review collisions
• Hint on homework 9.26




• The center of mass
  • concept
  • calculation applet
  • force and c.m. applet
    Example #1
    
  
  
• Momentum and collisions video



• Interactive Example 9-5
• Interactive Example 9-9


Chapter 10


• Rotation
  • subtended angles θ = s/r
  • angular velocity ω = v/r
  • angular acceleration α = a_t /r
  
  
  
  

gc6 7.20
The force as a function of time on a 0.060 kg tennis ball is depicted. What is the velocity of the ball after being struck if it was at rest initially?
A. 0.20 m/s
B. 2.0 m/s
C. 20 m/s
D. 200 m/s
Answer















sj6 QQ 9.10
Reading quiz A baseball bat is cut at the location of its center of mass as shown in the figure. The piece with the smaller mass is
A. the piece on the right
B. the piece on the left
C. Both pieces have the same mass.
D. impossible to determine.
Answer















sb5 9.42
M_Earth = 5.98×10²⁴ kg and M_Moon = 7.36×10²² kg. The distance between their centers is 3.84×10⁸ m. What is r_CM measured from the Earth's center?
A. 384,000 km
B. 4670 km
C. 3190 km
D. 6370 km
Answer















 



C. 20 m/s





















 



B. the piece on the left

The piece with the handle will have less mass than the piece made up of the end of the bat. To see why this is true, take the origin of coordinates as the center of mass before the bat was cut. Replace each cut piece by a small sphere located at the center of mass for each piece. The sphere representing the handle piece is farther from the origin, but therefore must have less mass than the end piece. In this way, the product of less mass and greater distance (for the handle) balances the product of greater mass and less distance (for the end piece).




















 



B. 4670 km