JEE MAINS PHYSICS QUESTION SEPTEMBER 2020
Answers
Answer:
(4)
Explanation:
please see attached pic
q -> A person pushes a box on a rough horizontal plateform surface. He applies a force of 200 N over a distance of 15m. Thereafter, he gets progressively tired and his applied force reduces linearly with distance to 100 N. The total distance through which the box has been moved is 30 m. What is the work
to 100 N. The total distance through which the box has been moved is 30 m. What is the work done by the person during the total movement of the box?
we have given the graph between force and displacement as shown in figure.
To find : work done by the person during the total movement of the box.
solution : we know, workdone , W = ∫F(x) dx
so work done is the area enclosed by the graph of force and displacement.
so, W = area enclosed by the graph
= area of rectangle [ 0 to 15 m ] + area of trapezium [ 15 m to 30 m]
= 200 N × 15m + 1/2 × (100 N + 200 N) × (30 - 15)m
= 3000 Nm + 150 N × 15 m
= 5250 Nm or 5250 J
Therefore the correct option is (1) 5250 J