15. A train travelling along a straight track starts from rest at point A and accelerates uniformly to 20 m s' in 20 s. It travels at this speed for 60 s, then slows down uniformly to rest in 40 s at point C. It stays at rest at C for 30 s, then reverses direction, accelerating uniformly to 10 min 10 s. It travels at this speed for 30 s, then slows down uniformly to rest in 10s when it reaches point B. Plot a graph of the motion of the train. b Use your graph to calculate
i the train's displacement from point A when it reaches a point C
ii the train's displacement from point A when it reaches point B
iii the train's acceleration each time its speed changes.

Alinearly polarized electromagnetic wave has an average intensity of 196 w/m^2. this wave is directed towards two ideal polarizers (in real polarizers, transmission is also effected by reflection and absorption). polarizer a is oriented with its transmission axis at an angle of θ_1=20.8∘ with the incident electric field. polarizer b has its axis at an angle of θ_2=63.0∘ with the incident electric field. what is the average intensity of the wave after it passes through polarizer a? what is the average intensity of the wave after it passes through polarizer b? suppose that the two polarizers a and b are interchanged. what would the average intensity be after passing through both polarizers?