Which statement about activation energy is true? a. it is not affected by catalysts. b. it has no effect on the rate of the reaction. c. it is the energy required to break existing chemical bonds. d. it is the same for all reactants.

An electric clothes dryer has a resistance of 8 ohms. it draws 30 a of current. what is the voltage, in volts, of the wall outlet that it is plugged into?

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) ! : )

If you held a stone over the mouth of a well and then let it go , what would happen to the stone? explain your answer.