Aboy yells in a narrow valley. the sound reflects off of a boulder that is 80 m away. how long will it take to hear the echo if the speed of a sound wave is 320 m/s?

Aboy with a mass 25 kg climbs into a small tree. he sits on a branch that is 2.o m above to the ground.what is his gravitational potential energy above the ground?

Sort the images based on whether there's a force of attraction or repulsion between the magnets shown. attraction repulsion

An object with initial temperature 130 ∘ f is submerged in large tank of water whose temperature is 50 ∘ f . find a formula for f ( t ) , the temperature of the object after t minutes, if the cooling constant is k = − 0.2 . remember newton's law of cooling (the rate of change of temperature with respect to time is equal to k times the difference between the temperature of the object and the surrounding temperature) ! : )