4. The kinetic energy (KE) and gravitational potential energy (PE) for an object are shown as functions of time in the graph on the right. What is the change in total mechanical energy of the object for the 5 seconds shown? (A) 0 J
(B) 2.5 J
(C) 5 J
(C) 5 J

Ablock of steel has a density of 0.29lbs per cubic inch. if the block has dimensions of 1 inch by 1 inch by 3 inches, what is its weight? a. 0.29lbs b. 0.58lbs c. 0.87lbs d. 1lbs

You throw a small rock straight up from the edge of a highway bridge that crosses a river. the rock passes you on its way down, 7.00 s after it was thrown. what is the speed of the rock just before it reaches the water 28.0 m below the point where the rock left your hand? ignore air resistance.

Scientific models are based on current knowledge, which can limit their effectiveness when new discoveries are made.