To penetrate armor, a projectile's point concentrates force in a small area, creating a stress large enough that the armor fails. a species of jellyfish launches a pointed needle that can penetrate the hard shell of a crustacean. the rapid deceleration on impact creates a 32 μn force on the tip, which has a very small 15 nm radius. how does this compare to the ultimate stress of steel?

Consider an ordinary, helium-filled party balloon with a volume of 2.2 ft3. the lifting force on the balloon due to the outside air is the net resultant of the pressure distribution exerted on the exterior surface of the balloon. using this fact, we can derive archimedes’ principle, namely that the upward force on the balloon is equal to the weight of the air displaced by the balloon. assuming that the balloon is at sea level, where the air density is 0.002377 slug/ft3, calculate the maximum weight that can be lifted by the balloon. note: the molecular weight of air is 28.8 and that of helium is 4.

What will a positive and a negative charge do if they are separated from each other?

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?