Gravitational Fields

Question 1

What is a gravitational field?

Answer 1

• A region where a mass experiences a force

Question 2

Define gravitational field strength?

Answer 2

• g = F / m

Question 3

What is newtons law of gravitation?

Answer 3

• F = Gm₁m₂ / r²

Question 4

Derive the equation g = Gm / r² for a point mass

Answer 4

• F = Gm₁m₂ / r² and g = F/m
• mg = Gm₁m₂ / r²
• g = Gm / r²

Question 5

What is the equation for gravitational potential?

Answer 5

• V_grav = -GM / r

Question 6

State the similarities between G fields and E fields

Answer 6

• Both obey the inverse square law F ∝ 1 / r²
• Both act over an infinite range
• Both fields are radial for point objects

Question 7

State the differences between G fields and E fields

Answer 7

• G fields are always attractive whilst E fields can be attractive or repulsive
• E fields are stronger than G fields
• E fields only act on charged particles whilst G fields act on all particles with mass
• E fields can be shielded (with a Faraday cage) whilst G fields cannot

Question 8

What might you need to combined with Newtons universal law of gravitation?

Answer 8

• Centripetal force equations such as F = mrω² or F = mv² / r

Question 9

Where is r measured from?

Answer 9

• THE CENTRE