CBSE Class 9 Answered
Since the ball is thrown at an angle, we have two parts to it's motion, it's horizontal motion and vertical motion, and when those are added we get the motion along the curved path - parabola.
During motion the force acting is the force of gravity, in the vertically downard direction.
Since the starting point and landing point lie on the same horizontal line, the displacement in the horizontal direction is finite and equal to the horizontal distance between the two points, but there is no force in horizontal direction, hence work is zero.
Also there is no net displacement in vertical direction, even though there is a force of gravity. Hence the work is also zero in vertical direction. Hence the total work done is zero.
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