Question

A girl having mass of 35 kg sits on a trolley of mass 5 kg. The trolley is given an initial velocity of 4 m s⁻¹ by applying a force. The trolley comes to rest after traversing a distance of 16 m.

Four men lift a 250 kg box to a height of 1 m and hold it without raising or lowering it. (g = 10 m s⁻²)

Compare the power at which each of the following is moving upwards against the force of gravity? (given g = 10 m s⁻²)

A group of students took an old shoe box and covered it with a black paper from all sides. They fixed a source of light (a torch) at one end of the box by making a hole in it and made another hole on the other side to view the sample taken in a beaker/glass tumbler as shown in the figure. They were amazed to see that milk taken in the glass was illuminated. They tried the same activity by taking a salt solution but found that light simply passed through it (a) Explain why the milk sample was illuminated. Name the phenomenon involved. (b) Same results were not observed with a salt solution. Explain. (c) Can you suggest two more solutions which would show the same effect as shown by the milk solution?