The mechanical advantage of a fixed pulley is always

Acave rescue team lifts an injured spelunker directly upward and out of a sinkhole by means of a motor-driven cable. the lift is performed in three stages, each requiring a vertical distance of 10.0 m: (a) the initially stationary spelunker is accelerated to a speed of 4.90 m/s; (b) he is then lifted at the constant speed of 4.90 m/s; (c) finally he is decelerated to zero speed. how much work is done on the 68.0 kg rescue by the force lifting him during each stage?

Because light travels in a straight line and casts a shadow, isaac newton hypothesized that light is

For waves in the ocean, the medium of the waves is a. air b. water c. energy d. a passing boat