C O N T A C T F O R C E S

 

C O N C E P T U A L  C H E C K  P O I N T

C O N T A C T     F O R C E S

Two boxes—one large and heavy, the other small and light—rest on a smooth, level floor.
You push with a force F on either the small box or the large box. Is the contact force between the two boxes (a) the same in either case, (b) larger when you push on the large box, or (c) larger when you push on the small box?

                

R E A S O N I N G   A N D     D I S C U S S I O N

Since the same force pushes on the boxes, you might think the force of contact is the same in both cases. It is not.

 What we can conclude, however, is that the boxes have the same
acceleration in either case—the same net force acts on the same total mass, so the same acceleration, a, results.

To find the contact force between the boxes, we focus our attention on each box individually, and note that Newton’s second law must be satisfied for each of the boxes, just as it is for the entire two-box system. 

For example, when the external force is applied to the small box,
the only force acting on the large box (mass m1 ) is the contact force; hence, the contact force must have a magnitude equal to (m1a) . 

In the second case, the only force acting on the small box (mass m2 ) is the contact force, and so the magnitude of the contact force is ( m2a ) . 

Since m1 is greater than m2 , it follows that the force of contact is larger when you push on the small box, m1a , than when you push on the large box, m2a .

To summarize, the contact force is larger when it must push the larger box.

A N S W E R

(c) The contact force is larger when you push on the small box.









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Solid State Physics  chap # 1 problems solution

(rk puri vk babber solid state physics book)

BOOKS

Basic Electronics  book by Pakistani author

Nuclear physics-1 book by Pakistani author

Nuclear physics complete book  by Pakistani author

Solid State Physics by M A Wahab 3rd ed,

Mechanics part 2 by indian author

Electricity and magnetism book by indian author

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