Newtons Second Law of Motion How fast does

Newton’s Second Law of Motion How fast does it go?

Acceleration • An unbalanced force causes something to accelerate.

Acceleration • Acceleration is directly related to the size of the force and the direction of the force. • It accelerates in the direction you push or pull it.

In other words…. Large Force = Large Acceleration F a

In other words…. Small Force = Small Acceleration F a So…. if you push twice as hard, it accelerates twice as much.

But there is a twist…. • Acceleration is INVERSELY related to the mass of the object.

In other words…. . using the same amount of force…. F Small acceleration Large Mass a Large acceleration F Small Mass a

Newton’s Second Law • Newton, that brilliant genius, observed those “rules” of acceleration and came up with his second law of motion. It is both a formula & a law.

Newton’s Second Law • The acceleration of an object is directly proportional to the net force & inversely proportional to it’s mass. • F = ma • Force = Mass x Acceleration

Okay then… • First, you need to know the units of Force, Mass & Acceleration. – The units used force are Newtons (N) – The units used for mass are kilograms (kg) – The acceleration units are meters per second squared (m/s 2).

Practice Problem 1 • An object is moving with an acceleration of 3 m/s 2 and has a mass of 55 kg. What force was applied to the object? • F = ma F = (55 kg)(3 m/s 2) F=? 2 F = 165 kg·m/s m=55 kg F = 165 N a=3 m/s 2

Practice Problem 2 • A force of 245 N is applied to an object. The object then accelerates at a rate of 4. 2 m/s 2. What is the mass of the object? • F=ma SO m=F/a F=245 N m = (245 N)/(4. 2 m/s 2) m=? m = 58. 33 kg a=4. 2 m/s 2