AST101 lecture 6: newtons laws

what is speed?

the rate of change of position (eg. how many km per hour)

what is velocity?

the speed and direction of an object (eg. the car is going due north at 60 km/hr)

what is acceleration?

the rate of change in velocity (any change in speed or direction, not just speeding up)

what is newton’s first law of motion?

an object in motion remains in motion unless acted upon by a force. conversely, an object at rest remains at rest unless acted upon by a force.

what is newton’s second law of motion?

acceleration is proportional to force and inversely proportional to mass (eg. more force = more acceleration, more mass = less acceleration)

what is newton’s third law of motion?

for every force there is always and equal and opposite reaction force

what is momentum?

mass x velocity, a heavier object moving with the same velocity as a lighter one has more momentum. momentum is always conserved in a closed system (eg. when you hit pool balls, the momentum from one is conserved in the next).

what is angular momentum?

mass x velocity x distance, angular momentum is always conserved in a closed system (eg. when you get closer to the sun, there is less distance, so speed must increase to maintain angular momentum)

what is newton’s universal law of gravitation?

there is force acting between any two objects in the universe

how does mass affect force in newton’s law of gravitation

doubling the mass of an object doubles the force, halving the mass halves the force

how does distance affect force in newton’s law of gravitation

doubling the distance reduces the force by a factor of 4, halving the distance increases force by a factor of 4 (d/2 = 2² x f, 2 x d = f/2²)

what is freefall?

when gravity is the only force acting on an object

how does object in space enter orbit around the earth?

if the speed of the object is equal to the force of gravity, they are in pereptual freefall around the earth

what is escape velocity?

the amount of speed needed to escape the pull of an objects gravity

what is escape velocity reliant on?

the mass of the object and the distance from the objects center (the farther away you are, the lower the escape velocity and vice verse)