Summary

• Newton's third law
• Motion in accelerating frames
• Circular motion

• Written Quiz    Timer
  
  
• Reading Quiz
  
  
• Work
  • physics definition
  • relative direction of F_net and d
    Example #1
    
    Example #2
    
    Example #3
    
  • kinetic energy
  
  

walker4e
Reading quiz Which of the forces in the car's free body diagram at the right can do work on the car?
A. 1
B. 2
C. 4
D. 1 and 3
E. 2 and 4
Answer















 
If you push a 25-kg box at constant speed for 3.0 m with a 150 N force, how much work have you done?
A. zero
B. 250 J
C. 450 J
D. 3750 J
Answer















 
If you twirl a 0.200-kg ball around your head with a radius of 1.0 m and a speed of 5.0 m/s, how much work is done each revolution?
A. zero
B. 5 J
C. 12.6 J
D. 31.4 J
Answer















 



D. 1 and 3

Only forces that have a component along the direction of motion can do work on the car.




















 



C. 450 J





















 



A. zero
The force is perpendicular to the distance!