newton's laws
an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a net external force
equation | symbol breakdown | meaning in words |
|---|---|---|
Fg = W = mg | Fg is force due to gravity, W is weight, m is mass, and g is the gravitational field strength (acceleration) which is 9.8 m/s² on Earth's surface. | the weight of an object is a long range force due to gravity; it is directly proportional to its mass and gravitational acceleration g |
common mistakes and misconceptions
mass is how much matter an object is made from; it is constant. the weight of an object is the force exerted by gravity on that object, so it depends on the local g value.
ex.: the value of g on the moon is much lower than on earth, so an object weighs less there, but the mass does not change.
the acceleration and net external force are directly proportional, and there is an inversely proportional relationship between acceleration and mass
an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by a net external force
equation | symbol breakdown | meaning in words |
|---|---|---|
Fg = W = mg | Fg is force due to gravity, W is weight, m is mass, and g is the gravitational field strength (acceleration) which is 9.8 m/s² on Earth's surface. | the weight of an object is a long range force due to gravity; it is directly proportional to its mass and gravitational acceleration g |
common mistakes and misconceptions
mass is how much matter an object is made from; it is constant. the weight of an object is the force exerted by gravity on that object, so it depends on the local g value.
ex.: the value of g on the moon is much lower than on earth, so an object weighs less there, but the mass does not change.
the acceleration and net external force are directly proportional, and there is an inversely proportional relationship between acceleration and mass
