An element's atomic number is 45. How many protons would an atom of this element have?

When air transfers energy to a cooler object what happens to the air temperature?

Does a star's apparent brightness depend only on its distance from earth?

A boy of weight 500 N has feet with a total area of 200 cm2 . What is the pressure between him and the ground if he stands on both feet?

A certain bridge is 4,224 feet long. What constant rate, in miles per hour, must be maintained in order to walk across the bridge in 12 minutes? (1 mile = 5,280 feet)

A spot of paint on a bicycle tire moves in a circular path of radius 0.33 m. When the spot has traveled a linear distance of 1.76m, through what angle has the tire rotated?

Luke and Carrie are driving down a straight section of the interstate at 70 mph in Luke's new convertible. Carrie is drinking a soda in the passenger seat.

A force produces power p by doing work w in a time t. what power will be produced by a force that does six times as much work in half as much time?

A batter hits a baseball with a bat. The bat exerts a force on the ball. Does the ball exert a force on the bat?

In a nuclear power plant, the temperature of the water in the reactor is above 100°C because of what?

Determine the total mechanical energy of a 250 g baseball if it has a velocity of 30 m/s when it leaves the pitcher's hand 1.2m above the ground.