past paper question notes- Gravitation Flashcards
Suggest quantitatively why it may be assumed that the sun is isolated in space from other stars? /2
- many stars around the sun
- net effect of forces is zero
features of geostationary orbit
1) Period of orbit is 24h
2) from west to east
3) above the equator
By reference to the pattern of the lines of the gravitational force near to the surface of the Earth, explain why the acceleration of free fall near to the Earth’s surface is approximately constant. /3
lines are radial
near the surface, the lines are parallel
parallel lines so constant field strength
so constant acceleration
Explain why at the surface of the planet, gravitational field strength is numerically equal to the acceleration of free fall? /1
a=f/m
and field strength= f/m
so they are equal
Explain why the gravitational potential energy of the rock is negative? /3
potential energy is zero at infinity
gravitational forces are attractive
work must be done on the rock to move it to infinity
State the relationship between gravitational potential and gravitational field strength? /2
gravitational field strength = - potential gradient
Suggest why for small changes in height near the Earth’s surface, gravitational potential is approximately constant? /2
height is much less than radius
radius approximately constant
A moon is in circular orbit around a planet.
Explain why the path of the moon is circular. /2
gravitational force provides centripetal force
centripetal force has constant magnitude
gravitational force is perpendicular to velocity
State one similarity and one difference between gravitational potential due to a point mass
and electric potential due to a point charge. /2
similarity: inversely proportional to the distance
difference: gravitational potential is always negative
electric potential can be positive or negative
