Question

6. In each situation described below, compare the magnitudes of the two forces. Explain your answer in each case.

a. A 90-kg an and a 60-kg boy each have one hand extended out in front and are pushing on each other. Neither is moving. Compare the force exerted by the man’s hand on the boy’s hand to that exerted by the boy’s hand on the man’s.

b. In (a), the boy begins to slide along the floor. Now compare the same two forces between their hands.

c. A person is leaning against a wall with her hand straight out pushing against the wall. Compare the force exerted by her hand on the wall to that exerted by the wall on her hand. What is the type of force exerted by the wall on her hand called?

d. In (c), is the force exerted by the wall on the person’s hand passive or active explain?

e. In (c) compare the horizontal component of the force exerted by the person’s feet on the floor to the horizontal component of the force exerted by the floor on her feet. What is the type of force exerted by the floor on her feet called?

f. Is the force describe in (e) that the person exerts on the floor passive or active? Explain.

Answer 1

Solution) (a) Here as neither the boy nor the man is moving so the force exerted by each other on each other is same that is the force exerted by man's hand on boy's hand is same as the force exerted by boy's hand on man's hand . So they exert equal forces .

Therefore forces are equal in this case.

(b) As the boy is sliding down so the man is exerting more force than boy .

So in this case the force exerted by man is greater than force exerted by boy .

(c) The force exerted by hand on the wall is equal to the force exerted by wall on the hand in magnitude but are opposite in direction . They form action reaction pair forces .

The force exerted by wall on her hand is called reaction force .

(d) The force exerted by wall on persons hand is passive force . As force exerted by wall is just in response to force exerted by person . So here the person is pushing so wall just responds to that persons force .

(e) Here also forces are equal in magnitude but opposite in direction .

The force exerted by floor on her feet is called reaction force .

(f) The force exerted by person on floor is active force .

Here the persons feet is exerting force on the floor and the floor is responding to it .

So it is active force .