Mass is measured in kilograms and describes the amount of matter and resistance to changes in motion. Weight is gravitational force and is measured in newtons. Use W=m×g with mass in kilograms and the supplied gravitational field strength in kgN. Convert grams to kilograms before multiplying.
Use exactly the value of g stated in the question; kg10N is a rounded exercise assumption. The same object has the same mass on Earth and the Moon but different weight because field strength differs. At one location, weight is proportional to mass. Near Earth’s surface, gravitational force acts approximately toward Earth’s centre.
Example 1
Find the weight of a 3kg object where g=kg10N.
W=3×10=30N.
Example 2
A 2kg object moves to a location with g=kg2N. Find its mass and weight there.
Mass remains 2kg. Weight =2×2=4N.
Watch out:Its mass stays the same. Its gravitational force is smaller because the Moon’s gravitational field is weaker.
Mass, weight and gravitational force practice | Year 7 Science | Ascent Arcade