A skateboarder is going to ride down one ramp and then up another. She wants to come down the first ramp and go up the second ramp to a height of exactly 3 m without kicking off or adding any other energy. Together the skateboard and skateboarder have a mass of 72 kg, and she will lose approximately 210 J of energy to friction. g = 9.8 m/s^2. Calculate the required starting height of the skateboarder in order for her to reach 3 m.

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?