a roller coaster car filled with passengers has a mass of 4.80 kg. what speed must it have at the top of the 7.5 m tall circular loop so the car doesn't fall off?

How do you calculate how dense the Earth is? I keep trying but I get 3.51*10¹⁰kg/m³. I don't know how or where I'm going wrong.

A toboggan is resting in the snow.

What two (equal in magnitude and opposite in direction) forces is the scale measuring when you start to pull on the toboggan but it remains stationary? Be specific.

Mass of Pecan: 1.47g

Mass of H2O: 50g

Initial temperature of water: 23°C

Final temperature of water: 59°C

Calculate the quantity of energy produced per gram of fuel (nut) burned.

What does this text suggest to you about the forces that inhibit or encourage an individual’s actions? 

Can a coefficient of friction be a whole number? Or does it have to be a decimal?

A 10kg sled slides down a frictionless icy hill at an angle of 25 degrees. Calculate the parallel component of the sled's weight. Calculate the acceleration of the sled.

Would b) require the force of gravity, or all forces of gravity (parallel, perpendicular, regular, etc)?

A car breaks on an icy road. At a point, the car's brakes apply a force before the car skids. 

Would this be calculating the coefficient of static or kinetic friction?

The solutios to nx²+px+q=0 are 4 and -2\5 what information does this tell you about the graph of f(x)=nx²+px+q

A vehicle collision produced -1250N net force. What is the acceleration of a 55.0 kg passenger in the car?