In the Bohr model of the atom, electrons exist in fixed orbits and they cannot move from one level to another. True False

Explain the law of conservation of mass. When wood burns, it releases heat and turns into ashes. When the ashes are weighed, they are significantly lower than that of the wood. How is this possible in terms of the law of conservation of mass?

Why poison frogs don't poison themselves? Are frogs dangerous?

Which of the following statements is true? A. A 140-lb. person would weigh more than 140 lbs on the moon because of the increase in gravity. B. Earth has a synchronous rotation, when means its rotation and revolution periods are the same length. C.

A planet has two moons. The first moon has an orbital period of 1.262 Earth days and an orbital radius of 2.346 x 104 km. The second moon has an orbital radius of 9.378 x 103 km. What is the orbital period of the second moon?

Why was it difficult for Dalton to prove his theory? a. People did not believe that solids could be made of small particles c. Only very powerful, expensive microscopes could be used in his experiments b. Atoms are too small to see d.

A flight attendant pulls a 60.0 N flight bag a distance of 239.0 m along a level airport floor at a constant speed. A 21.0 N force is exerted on the bag at an angle of 66.0 degrees above the horizontal. How much work is done on the flight bag?

A girl throws a rock horizontally, with a velocity of 10 m/s, from a bridge. It falls 20 m to the water below. How far does the rock travel horizontally before striking the water?

This is a machine consisting of two wheels of different sizes that rotate together. It is a modified lever.

A source from which organisms generally take elements is called a/an A. biotic community. B. reservoir. C. exchange pool. D. food web.

Jill has a mixture of sand and iron fillings. The mass of the mixture is 250 g. Jill uses a magnet to seperate the two substances. Then she measures the mass of the sand as 150 g what should be the mass of the iron fillings