A boy and his skateboard have a combined mass of 60kg. After an initial shove, the boy starts coasting at 5.5m/s along a lever driveway. Friction brings him to a stop in 5.0 s. If the combined force of gravity on the boy and skateboard is 590 N, what is the average coefficient of (rolling) friction between the driveway and the skateboard wheels?

Astudent is given an assignment to demonstrate diffraction. he takes a photograph of a straw in a glass of water. the straw appears bent at the water level. which best describes this example? a) this is a good example of diffraction. b) this is an example of dispersion and not diffraction. c) this is an example of refraction and not diffraction. d) this is an example of reflection and not diffraction.