Summary

• Spring potential energy
• Conservation of mechanical energy
• Friction & nonconservative work

• Class Quiz
  
  
• Written Quiz    Timer
  
  
• Reading Quiz
  
  
• Momentum
  • definition, units, vectors
  • Newton's second law
  
  
• Conservation of momentum
  • no external forces
    Example #1
    
  • impulse
    Example #2
    
  • graphical interpretation
  • air bags
  
  
  
  

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



























walker4
Reading quiz 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















sb5 9.4
A 40 kg child on frictionless skates throws a 0.50 kg stone with speed 5.0 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















sj6 9.10
A tennis player receives a 50 m/s shot with the 0.06 kg ball and returns it at 40 m/s. 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















 



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.




















 



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.




















 



B. 6.25 cm/s





















 



C. 5.40 kg·m/s