Answer:
Andy’s car rolls down a hill with the engine off.
A balloon expands as it is heated by the Sun.
Explanation:
Work is said to be done when a force applied on an object is able to move/displaces the object from its position. But, if force is applied on an object but it does not move or force which is being applied on the object is prependicular to the object in such situations work done is zero.
The formula for work done is mentioned as under:
W = F.d. cosФ
Where, W = Work done
F = Force applied
d = displacement
Ф = angle between force and displacement
So if Ф = 90° then cosФ = 0 and hence, W = F.d. cosФ = F x d x 0 = zero &
W = F.d. cosФ = F x 0 x cosФ = zero, when d = 0.
Andy’s car rolls down a hill with the engine off - In this situations work is said to be done because there is a net movement of the object in the direction of force.
A balloon expands as it is heated by the Sun - In this situation work is said to be done due to heat expansion.
Hannah leans against her locker, but it doesn’t move, a wind turbine stands still on a sunny, windless day & James pedals a stationary exercise cycle that doesn’t move - In all these situations, work done is zero because there is no net displacement. i.e. d = 0.
