Which of the following is the best example of a proper hypothesis? a) i think there is no effect on sleep if you are on your phone at night. b) dogs that get treats behave better. c) if cat litter a and b are tested on the same cat, then cat litter a will clump better than b. d) pizza is a better dinner choice than doughnuts.

Avery hard rubber ball (m = 0.5 kg) is falling vertically at 4 m/s just before it bounces on the floor. the ball rebounds back at essentially the same speed. if the collision with the floor lasts 0.05 s, what is the average force exerted by the floor on the ball?

Suppose a comet has an orbital period of 309.1 years around the sun. what is it’s average distance from the sun?

An ice-making machine inside a refrigerator operates in a carnot cycle. it takes heat from liquid water at 0.0 degrees celsius and rejects heat to a room at a temperature of 19.2 degrees celsius. suppose that liquid water with a mass of 76.3kg at 0.0 degrees celsius is converted to ice at the same temperature. take the heat of fusion for water to be l_f = 3.34*10^5 j/kg.how much energy e must be supplied to the device? express your answer in joules.