Summary

• Energy diagrams
• Nonconservative work
• Center of mass

Bonus question Chs.07-08



• Linear momentum
• definition
• Newton's 2^nd law
• conservation of momentum
Example #1


• Impulse
• graphical interpretation
• air bags
Example #2
Example #3





• Momentum & collisions
• collision balls applet

• elastic collisions
• inelastic collisions

gc6 6.q10
Water balloons are tossed from the roof of a building, all with the same speed but with different launch angles. Which one has the highest speed on impact? (Ignore air friction.)
A
B
C
D. All land with the same speed.
Answer



















sb5 9.4
A 40.0-kg child on frictionless skates throws a 0.500-kg stone with a speed of 5.00 m/s. What is the recoil speed of the child?
A. 16.0 mm/s
B. 6.25 cm/s
C. 100 m/s
D. 16.0 m/s
Answer



















walker4
A net force of 200 N acts on a 100-kg boulder, and a force of the same magnitude acts on a 0.100 kg pebble. The change of the boulder's momentum in one second is ______ the change of the pebble's momentum in the same time period.
A. greater than
B. less than
C. equal to
Answer



















PoP5 8.10a
A tennis player receives a shot with the 0.0600-kg ball traveling horizontally at 50.0 m/s and returns the shot with the ball traveling horizontally at 40.0 m/s in the opposite direction. What is the impulse delivered to the ball?
A. 0.60 kg·m/s
B. 1.67 kg·m/s
C. 5.40 kg·m/s
D. 18.5 kg·m/s
Answer







































answer

D. All land with the same speed.
The total energy is the same for each ball, and each converts all of its energy to kinetic upon landing, so all land with the same speed.



















answer

B. 6.25 cm/s




















 



C. equal to

Equal force over an equal time period means an equal impulse, and that implies an equal change in momentum. The change in speed of the boulder, however, is much less than that of the pebble.
























answer

C. 5.40 kg·m/s