3.2 Newton's law of gravitation Flashcards
State the inverse square law
F is proportional to 1/r^2
What is the equation for Newton’s law of gravitation
F = Gm1m2/r^2
What is G in Newton’s law of gravitation
The gravitational constant
Why is G very difficult to measure in a laboratory
Gravitational forces are very small unless one of the ‘particles’ is a planet or a star
What is the value of the gravitational constant
6.67 x 10^-11 Nm^2kg^-2
What is meant by r in the newton’s law of gravitation equation
The distance r is to the centre of the object
What does it mean to be in a state of free fall
Where a body is only experiencing the force of the pull of the earth, it is said to be in a state of free fall
What is the Earth’s only natural satellite
The moon
What are the forces acting on satellites and what does this mean for its state while orbiting the earth
Satellites only have the force of the earth’s pull acting on them, so they are said to be in a state of constant free fall
What is the equation when you combine newton’s second law and newton’s law of gravitation
r^3 = GmeT^2/4pi^2
What is kepler’s third law and what does this mean for the distance of the satellite with relation to time
r^3 is proportional to T^2 since Gme/4pi^2 is a constant. this means that the further out a satellite is, the longer it takes to orbit the earth
For moons orbiting other planets in orbits of known radius, what do we need to observe in order for us to calculate the mass of the planet and what is the equation for this
We need to observe the moon’s period of revolution and the equation for this is mp = 4pi^2r^3/GT^2
Is weightlessness really what it seems
Not really as an astronaut will be able to float in space but his weight will still be acting on him all the time
