Summary

• Three kinds of friction
• Newton's Second Law
• Newton's third law

• Class Quiz
  
  
• Reading Quiz
  
  
• Motion in accelerating frames
  Example #1
  Example #2
  
  
• Circular motion
  • centripetal acceleration
    • centripetal force
      string break applet
      Example #3
      Example #4
      Example #5
      curvey road applet
      carousel applet
      
      
    • centrifugal force
      Example #6
      Example #7
      Example #8
      
    
    
  • Interactive Example 6-3
  • Interactive Example 6-6
  • Interactive Example 6-8
  
  
  
  

KW3tb
If you push on a railroad boxcar with a force of 200 N and it doesn't move, you can conclude that
A. you are unable to overcome the boxcar's inertia.
B. your force is canceled by the third law force.
C. the boxcar has too much mass to accelerate.
D. there is another force of 200 N on the boxcar in the opposite direction.
Answer















wk4 6.cq.19
Reading quiz The gas pedal, the brake pedal, and the steering wheel can all accelerate a car.
A. True
B. False
Answer















gc6 4.15
A person stands on a scale in an elevator. The scale briefly reads only 0.75 of the person's regular weight. What is the acceleration of the elevator?
A. 2.45 m/s² up
B. 2.45 m/s² down
C. 7.35 m/s² up
D. 7.35 m/s² down
Answer















Wlk4 5.41
When on solid ground your weight is 632 N. In an elevator your apparent weight is 538 N. What are the direction and magnitude of the elevator's acceleration?
A. −1.46 m/s²
B. 1.46 m/s²
C. −18.2 m/s²
D. 18.2 m/s²
Answer















 
A 60-kg person on a merry-go-round is traveling at 4.0 m/s around a 2.0-m circle. What is the acceleration of the person?
A. zero
B. 8.0 m/s² in
C. 2.0 m/s² in
D. 8.0 m/s² out
Answer















 
What is the centripetal force on the person?
A. 480 N in
B. 800 N in
C. 600 N in
D. 600 N out
Answer















sj6 4.30
At what rate should astronauts be rotated on a 10.0 m arm to experience an acceleration of 1.40g?
A. 5.67 rpm
B. 7.82 rpm
C. 0.295 rpm
D. 11.2 rpm
Answer















sj6 6.19b
A 500 kg roller coaster goes over a hill of radius 15.0 m. What is the max speed to stay on the track?
A. 24.7 m/s
B. 32.2 m/s
C. 7.32 m/s
D. 12.1 m/s

Answer















sj6 6.18
A 0.40 kg ball is swung in a vertical circle of radius 0.50 m. If v = 4.0 m/s at the top, what is the string tension there?
A. 8.88 N
B. 12.8 N
C. 3.92 N
D. 16.7 N
Answer















sj6 6.26
At what Earth rotation period would an object at the equator have zero apparent weight? R_E = 6370 km.
A. 22.6 h
B. 1.41 h
C. 12.2 h
D. 0.117 h
Answer















 



D. there is another force of 200 N on the boxcar in the opposite direction.

The other force is the force of static friction on the boxcar.




















 



A. True

Any change in velocity, either speed or direction, requires an acceleration. All of these change either the speed or the direction of the car's travel.





















 



B. 2.45 m/s² down





































 



A. −1.46 m/s²


























 



B. 8.0 m/s² in













 



A. 480 N in













 



D. 11.2 rpm













 



D. 12.1 m/s













 



A. 8.88 N













 



B. 1.41 h