# Physics Problems

• Down in a deep coal mine, a mile or so below the surface of the earth, is the force of gravity more or less than that at the entrance to the mine up at ground level? (Assume the Earth has a uniform density, and ignore any centrifugal and centripetal forces).

• A man holds a rifle horizontally 6 feet above the ground. At the moment he fires it, another bullet is dropped from the same height, 6 feet.

Ignoring frictional effects and the curvature of the earth, which bullet hits the ground first?

• Pour hot water into a thick drinking glass and into a thin wine glass. Which glass in more likely to crack? And why?

• A ball, a disc and a ring, each 5 inches in diameter, sit at the top of an inclined plane. If all three objects start rolling down the incline at the same instant, which one will reach the bottom first? (Assume that they all roll efficiently that is, they are perfectly formed and don't wobble--and ignore any effect of air resistance and friction.)

• The speed of sound in air is about 740 miles per hour. Suppose that a police car is sounding its siren and is driving towards you at 60 miles per hour. At what speed is the sound of the siren approaching you?

• Rupert is sailing a plastic boat in his bathtub. The boat is loaded with nuts, bolts and washers. If Rupert dumps all these items into the water. allowing his boat to float empty, will the water level in the bath rise or fall?

• It is generally accepted that matter expands with increasing temperature, and contracts with decreasing temperature. There is one notable exception. Which is it, and why has nature provided for it?

• How could you make a raw egg float halfway between the surface and the bottom of a glass of water?

• An ice cube is floating in a beaker of water, with the entire system at 0º Centigrade(32ºF). Just enough heat is applied to melt the ice cube without raising the temperature of the system. What happens to the water level in the beaker? Does it rise, fall, or stay the same?