Why do helium balloons float? Talk about density of atoms and compare to elements in the air.

How long does it usually take a hypothesis to become a theory

How much heat is absorbed by a 125 g sample of water when it is heated from 25.20 ºc to 32.80 ºc? the specific heat of water is 4.184 j/g ºc?

We want to hang a thin hoop on a horizontal nail and have the hoop make one complete small-angle oscillation each 2.0 s. What must the hoop's radius be?

The angular velocity in rad/s if the minute hand of a watch is:

What happens after a new moon

Two lab carts are pushed together with a spring mechanism compressed between them. Upon release, the 5.0 kg cart repels one way with a velocity of 0.12 m/s. The 2.0 kg cart goes the other way. At what velocity does it travel?

A bowling ball has a mass of 7.2 kg and a weight of 70.6 N. It moves down the bowling alley at 1 m/s and strikes a pin with a force of 15.0 N. What is the force that the pin exerts on the bowling ball?

an electric clothes dryer has a resictance of 16 Ohms it drawes 15 A of current what is the voltage in volts of the wall outlet that it is pluged into

A lorry with a mass of 5000kg accelerates to overtake a caravan on the motorway. Its acceleration is 1.5m/s². What force must the engine be providing? You can ignore the effects of friction and air resistance

Norma kicks a soccer ball with an initial velocity of 10.0 meters per second at an angle of 30.0% if the ball moves though the air for 3.2 seconds what's the horizontal distance traveled by the ball