Answer:
The acceleration of the car at the instant when t=3s is found by taking the gradient of the tangent at the point t=3.
The tangent are those dotted lines sloping upwards in the graph.
Tangent: A straight line that touches the curve and does not intersect it.
The reason why they wrote instantaneous is because the acceleration (or gradient of graph) is not constant throughout hence it is just at the moment when t=3s.
Gradient is used to find the acceleration of a speed time graph.
Explanation:
Work done by gravity is given by the formula,
W = ......... (1)
It is known that when levels are same then height of the liquid is as follows.
h = ......... (2)
Putting value of equation (2) in equation (1) the overall formula will be as follows.
W =
=
= 0.689 J
Thus, we can conclude that the work done by the gravitational force in equalizing the levels when the two vessels are connected is 0.689 J.