Gravitational Field Flashcards
State Newton’s Law of Gravitation
The mutual force of attraction between any two point masses is directly proportional to the product of their masses and inversely proportional to the square of the separation between their centers.
Define Gravitational field
Gravitational field is a region of space surrounding a body in which another body placed in it experiences a gravitational force due to its mass.
Define Gravitational potential energy
It is the work done by an external agent in bringing a point mass from infinity to that point.
Define Gravitational Field Strength
It is the Gravitational force exerted per unit mass on a small test mass placed at that point.
Define Escape velocity
It is the minimum velocity an object must have to start to escape from the gravitational influence of the Earth.
Explain why is there a negative sign in the expression u= -GMm/r
U at infinity is taken to be 0 and WD by external force is negative. Thus the object loses GPE from 0 and the GPE is negative. (Object is brought FROM infinity to point mass)
Define Gravitational Potential
It is the work done per unit mass by an external agent in bringing a small test mass from infinity to that point.
State Kepler’s third law
It states that square of the period of the object in circular orbit is directly proportional to the cube of the radius of its orbit.
Explain why an astronaut in an orbiting satellite may be described as weightless.
The only force experienced by the astronaut will be Gravitational force due to earth. Astronaut and satellite will be falling freely with the same acceleration. As there are no other forces acting on the astronaut he is deemed to be experiencing weightlessness.
