22.A man drags a box with uniform speed across a 10 mrough floor. The

1.	22.A man drags a box with uniform speed across a 10 mrough floor. The coefficient of friction of the floor is0.5. If the man pulls the box with a force of (v3) kNat an angle 30° with the horizontal, the work done indragging the box is(1) 30 kJ(3) 10 3 r kJ(2) 15 kJ(4) 5 kJ
Answer» Here , we actually need to know which work are we talking about , there can be work done by1) frictional force - this work will be negative as the direction of the frictional force will be opposite to the side of movement , so W=F. d = F d cos(theta) = Fdcos180= -Fd 2) force applied externally, whose component to the side of movement or horizontal will be 3-2x cos 30= 3-2x3-2/2= 3/2 kN now since work done = fdcos(theta)= 3/2 x 10 x cos 0= 15 kJ

22.A man drags a box with uniform speed across a 10 mrough floor. The coefficient of friction of the floor is0.5. If the man pulls the box with a force of (v3) kNat an angle 30° with the horizontal, the work done indragging the box is(1) 30 kJ(3) 10 3 r kJ(2) 15 kJ(4) 5 kJ

Answer»

Here , we actually need to know which work are we talking about , there can be work done by1) frictional force - this work will be negative as the direction of the frictional force will be opposite to the side of movement , so W=F. d = F d cos(theta) = Fdcos180= -Fd

2) force applied externally, whose component to the side of movement or horizontal will be 3-2x cos 30= 3-2x3-2/2= 3/2 kN

now since work done = fdcos(theta)= 3/2 x 10 x cos 0= 15 kJ

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22.A man drags a box with uniform speed across a 10 mrough floor. The coefficient of friction of the floor is0.5. If the man pulls the box with a force of (v3) kNat an angle 30° with the horizontal, the work done indragging the box is(1) 30 kJ(3) 10 3 r kJ(2) 15 kJ(4) 5 kJ

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