What is a household object that refracts light

The crank oa rotates in the vertical plane with a constant clockwise angular velocity ω0 of 5.6 rad/s. for the position where oa is horizontal, calculate the force under the light roller b of the 10.6-kg slender bar ab.

If the ama of the inclined plane below is 2, calculate the ima and efficiency. ima = efficiency =

What sort of waves exhibit the doppler effect?