Why does a helium balloon rise in the air while an ordinary balloon filled with air does not?

Why did scientists develop modles of atoms?

Why do scientists agree to use one system of measurement

What causes the different season on earth

A pair of scissors is a complex machine. What are the simple machines you need, to make a pair of scissors?

Which set of terms best defines what affects kinetic energy and potential energy, respectively? Choose one best answer

Two masses are separated by 1 m. suppose the masses are moved so they are 2 m apart how will the gravitational force change

Bob rubs a piece of fur on a hand rubber rod, giving the rod a negative charge. what happens?

The period of a simple pendulum is 3.8 s. the length of the pendulum is doubled. what is the period t of the longer pendulum? t = s

True or false - sound waves can travel across outer space.

In which one of the following locations can a person hear the echo of a sound? a. At least 33.2 meters behind the reflecting surface b. Less than 16.6 meters in front of the reflecting surface c. Less than 33.2 meters behind the reflecting surface d.