Most common digital timers display in both minutes and seconds. You use a timer to test how long your electric toothbrush runs for one brushing cycle. If s is the number of seconds it takes for one full brushing cycle, and m is the number of minutes it takes for the same brushing cycle, then write an equation expressing a relationship between s and m.

Spend time observing or thinking about events that involve matter and energy. which events can you explain? which events can’t you explain?

Aperson stands on a platform, initially at rest, that can rotate freely without friction. the moment of inertia of the person plus the platform is ip. the person holds a spinning bicycle wheel with its axis horizontal. the wheel has moment of inertia iw and angular velocity ωw. take the ωw direction counterclockwise when viewed from above. part a what will be the angular velocity ωp of the platform if the person moves the axis of the wheel so that it points vertically upward?

Apulley system is used to lift a 2,000 newton engine up a distance of 3 meters. the operator must apply a force of 250 newtons to the chain of the pulley system to lift the motor. to lift the engine 3 meters, the operator must pull a total of 30 meters of chain through the pulley system. what is the value of di?