16. A common experience is to find that a steady pull is required to keep an obj

Question

16. A common experience is to find that a steady pull is required to keep an object moving, even on a level surface with friction present. Analyzing this experience in light of the laws of motion, the accepted conclusion is that:

A. your pull is canceled by the third law reaction force.

B. the laws of motion do not apply where there is friction.    

C. the laws of motion only apply when you start pulling or stop.

D. the object is really accelerating but it is not apparent.

E. a frictional force exactly opposes your pull and the first law applies.

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17. A net horizontal force of 200 N acts on a 50 kg cart, which is free to roll on a level surface.

A. The cart accelerates at 0.25 m/s2.

B. The cart accelerates at 10000 m/s2.    

C. The cart does not accelerate because it pushes back on the person with a force of 200 N.

D. The cart accelerates at 4 m/s2.

E. The cart accelerates at 10 m/s2.

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18. A 5.0 kg block on a smooth horizontal surface is acted upon by two forces: a horizontal force of 40 N acting to the right and a horizontal force of 10 N to the left. The acceleration of the block will be:

A. 5.0 m/s2 to the right

B. 6.0 m/s2 to the right    

C. 10.0 m/s2 to the right

D. 8.0 m/s2 to the right

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19. A 7.0-kg block being pulled across a table by a horizontal force of 45 N also experiences a frictional force of 10 N. What is the acceleration of the block?

__________ m/s2

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20. A 100 pound sack of potatoes falls from an airplane. As the velocity of the falling sack increases, so does the air resistance on it. When the air resistance equals 100 pounds, the acceleration of the sack will be:

A. 9.8 m/s2.

B. zero.    

C. 9.8 m/s.

D. infinite.

Explanation / Answer

16.d

17.c

18.d

19.a

20.b

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