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A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in Fig. 5.19. What is the action on the floor by the man in the two cases? If the floor yields to a normal force of 700 N, which mode should the man adopt to lift the block without the floor yielding?

A block of mass 25 kg is raised by a 50 kg man in two different ways as shown in Fig.
5.19. What is the action on the floor by the man in the two cases? If the floor yields to a
normal force of 700 N, which mode should the man adopt to lift the block without the
floor yielding?
 

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Grade:12th pass

3 Answers

Prithvi Raj
34 Points
9 years ago
For this type questions the idea is to find the net force on floor.
In the first case the man apply a force of (25X10)N upward to lift the block, so by newtons 3rd law a eqal and opposite force acts on floor = 25x10 N  so including the man’s weight it self we get a total of (25+50)x10 N force on floor.
in the second case in order to pull the body up by means of a pully he must apply a net force eqal to weight of body in downward direction there for floor will provide an eqal and opposite force upward there for net force on the floor = (50-25)x10 N, by doing this calculations we get first one as a force greater than 700N and second one leass than 700N, since the floor can only give a force of 700 N back the man should adopt the second method.  here I have takes value of “g” as 10 insted of 9.8
Priyanka
18 Points
9 years ago
Thank u so much for answering....
Jishan
11 Points
6 years ago
As we know that in second case we can see there is apply and the body is being pulled so there the fnet will be 50-25(10) N and in the first case the fnet will be 50+25(10) N. As comparing the force required in case 1 is greater than case2

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