Cards | 10 |

Focus | Newton's Laws |

Topics | Acceleration, First Law of Motion, Law of Universal Gravitation, Second Law of Motion, Third Law of Motion |

Newton's second law of motion leads to the formula for acceleration which is a measure of the rate of change of velocity per unit time and, if you solve for positive acceleration, reveals how much net force is needed to overcome an object's mass. The formula for acceleration is \(\vec{a} = { \vec{F} \over m }\) or, solving for force, \(\vec{F} = m\vec{a}\).

Also known as the **law of inertia**, Newton's first law of motion states that *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 an unbalanced force.*

Newton's law of universal gravitation defines **gravity**: *All objects in the universe attract each other with an equal force that varies directly as a product of their masses, and inversely as a square of their distance from each other. *Expressed as a formula: \(\vec{F_{g}} = { Gm_{1}m_{2} \over r^2}\) where r is the distance between the two objects and G is the **gravitational constant** with a value of 6.67 x 10^{-11}.

Newton's second law of motion states that *The acceleration of an object as produced by a net force is directly proportional to the magnitude of the net force, in the same direction as the net force, and inversely proportional to the mass of the object.* This law basically means that the greater the mass of an object, the more force is needed to overcome its inertia.

Newton's third law of motion states that *For every action, there is an equal and opposite reaction. *When an object exerts a force on another object, the second object exerts a force of equal magnitude in the opposite direction on the first object.