Explain two negative effects of friction

The uniform slender bar rests on a smooth horizon- tal surface when a force f is applied normal to the bar at point a. point a is observed to have an initial acceleration aa of 20 m/s2, and the bar has a corre- sponding angular acceleration of 18 rad /s2. deter- mine the distance b.

What is the relationship between wavelength of light and the quantity of energy per photon?

A: all waves on the electromagnetic spectrum travel at the same speed in a vacuum. the speed of these waves in a vacuum is 3x108 m/s. as the wavelength of a wave doubles, how does the speed and frequency of the wave change?