A region of space where a test mass experiences a force due to the gravitational attraction of another mass
The Earth's gravitational field produces an attractive force. The force of gravity is always attractive
The force per unit mass experienced by a test mass at that point
A person’s weight on Jupiter would be so large that a human would be unable to fully stand up
Calculate the mass of an object with weight 10 N on Earth.
The mean density of the Moon is 3/5 times the mean density of the Earth. The gravitational field strength on the Moon is 1/6 of the value on Earth.
Determine the ratio of the Moon's radius rM and the Earth's radius rE.
There is a big difference between g and G (sometimes referred to as ‘little g’ and ‘big G’ respectively), g is the gravitational field strength and G is Newton’s gravitational constant. Make sure not to use these interchangeably! Remember the equation density ρ = mass m ÷ volume V, which may come in handy with some calculations
A planet is equidistant from two stars in a binary system. Each star has a mass of 5.0 × 1030 kg and the planet is at a distance of 3.0 × 1012 m from each star. Calculate the magnitude of the resultant gravitational field strength at the position of the planet.
Step 1: List the known quantities
Step 2: Write out the equation for gravitational field strength
Step 3: Calculate the gravitational field strength due to one star
g = 3.7 × 10−5N kg−1
Step 4: Resolve the vectors vertically
Step 5: Use vector addition to determine the resultant gravitational field strength
gresultant = g cos 42° + g cos 42° = 2g cos 42°
gresultant = 2 × (3.7 × 10−5) × cos 42°
gresultant = 5.5 × 10−5 N kg−1
Don't worry, for calculation questions involving resultant gravitational field strength - only two bodies along a straight line will be tested!
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