1. Mass and Acceleration

2. Mass  Matter has substance. Solids, liquids or gasesSolids, liquids or gases Subatomic particlesSubatomic particles Planets and starsPlanets and stars  We feel the weight of different objects.  We will see that weight is not mass, but mass can have weight.  Mass measures the amount of matter in an object.

3. Mass Units  Mass is measured in kilograms. 1 kg = 1000 g1 kg = 1000 g 1 atomic mass unit (about the mass of one hydrogen atom) = 1.66 x 10 -27 kg1 atomic mass unit (about the mass of one hydrogen atom) = 1.66 x 10 -27 kg  Mass is a scalar. Mass times a vector gives another vectorMass times a vector gives another vector For instance, momentum:For instance, momentum:

4. Force and Acceleration  With force there is acceleration.  The amount of acceleration depends on the mass.  The direction of the force and acceleration are the same.

5. Force Units  Force is mass times acceleration.  The dimensions of force are M(L/T 2 ).  In SI units a newton (N) = 1 kg m / s 2.

6. Law of Action 2 The change in motion is proportional to the force and the change is made in the same direction as the force.  A force gives rise to action by acceleration.  Force = mass x acceleration (Newton’s second law). Rocket: has mass Force: becomes acceleration Initial velocity Final velocity: changed by the force

7. Accelerating a Mass  A loaded 747 jet has a mass of 3.6 x 10 6 kg and four engines.  It takes 1700 m at constant thrust (force) to reach a takeoff speed of 86 m/s (310 km/h).  What is the force per engine?  The distance and final velocity are used to get the acceleration.  The acceleration and mass give the force.  F = (7.8 x 10 6 N)/4 = 2.0 x 10 6 N.

8. Vector Force  A 1000 kg satellite in space is moving at 5 km/s when a rocket fires with a thrust of 5 x 10 3 N at 60° to the direction of motion.  The rocket fires for 1 minute. Where does it move after firing?  The force and acceleration are vectors.  Pick x in the direction of initial motion.  The new velocity is  v x = 5.1 km/s, v y = 0.26 km/s. next x 