Mass and MotionMassMass UnitsForce and AccelerationForce UnitsSecond Law: Law of AccelerationVector ForceChange in VelocityMass and MotionMass and MotionMassMassMatter has substance.Matter has substance.•Solids, liquids or gasesSolids, liquids or gases•Subatomic particlesSubatomic particles•Planets and starsPlanets and starsWeight is not mass, but mass can have weight.Weight is not mass, but mass can have weight.Mass measures the amount of matter in an object.Mass measures the amount of matter in an object.Mass UnitsMass UnitsMass is measured in Mass is measured in kilograms.kilograms.•1 kg = 1000 g1 kg = 1000 g•1 atomic mass unit (about 1 atomic mass unit (about the mass of one hydrogen the mass of one hydrogen atom) = 1.66 x 10atom) = 1.66 x 10-27-27 kg kgPounds measure weight (a Pounds measure weight (a force) not mass.force) not mass.© R. Rathe, NISTForce and AccelerationForce and AccelerationWith force there is acceleration.With force there is acceleration.The amount of acceleration The amount of acceleration depends on the mass.depends on the mass.Mass is a scalar.Mass is a scalar.•Mass times a vector gives another Mass times a vector gives another vector.vector.•The direction of the force and The direction of the force and acceleration are the same.acceleration are the same.mFaamFForce UnitsForce UnitsForce is mass times acceleration.Force is mass times acceleration.The dimensions of force are M(L/TThe dimensions of force are M(L/T22).).In SI units a newton (N) = 1 kg m / sIn SI units a newton (N) = 1 kg m / s22..Second Law: Law of Second Law: Law of AccelerationAcceleration2The change in motion is proportional to the net force The change in motion is proportional to the net force and the change is made in the same direction as the and the change is made in the same direction as the net force.net force.Net force gives rise to acceleration.Net force gives rise to acceleration.Force = mass x acceleration (Newton’s second law).Force = mass x acceleration (Newton’s second law).Rocket: has massForce: becomes accelerationInitial velocityFinal velocity: changed by the forceVector ForceVector ForceA 1000 kg satellite in A 1000 kg satellite in space is moving at 5.0 space is moving at 5.0 km/s when a rocket fires km/s when a rocket fires with a thrust of 5.0 x 10with a thrust of 5.0 x 1033 N N at 60at 60°° to the direction of to the direction of motion.motion.The rocket fires for 1 The rocket fires for 1 minute. Where does it minute. Where does it move after firing?move after firing?Identify the quantities in the Identify the quantities in the problem:problem:•Mass, Mass, m m = 1000 kg= 1000 kg•Initial velocity, Initial velocity, vv00 = 5 x 10 = 5 x 1033 m/s m/s•Force, Force, FF = 5 x 10 = 5 x 1033 N at 60 N at 60°° •Time, t = 1 min = 60 sTime, t = 1 min = 60 sForce and velocity are vectorsForce and velocity are vectors•Pick Pick xx in the direction of initial in the direction of initial motion: motion: vvxx = = vv00 . .•FFxx = = FF cos cos•FFyy = = FF sin sinx= 60F = 5000 NChange in VelocityChange in VelocityA 1000 kg satellite in A 1000 kg satellite in space is moving at 5.0 space is moving at 5.0 km/s when a rocket fires km/s when a rocket fires with a thrust of 5.0 x 10with a thrust of 5.0 x 1033 N N at 60at 60°° to the direction of to the direction of motion.motion.The rocket fires for 1 The rocket fires for 1 minute. Where does it minute. Where does it move after firing?move after firing?The force gives acceleration.The force gives acceleration.•aaxx = = FFxx / /mm = ( = (FF//m)m) cos cos•aayy = = FFyy / /mm = ( = (FF//m)m) sin sinThe change in velocity is due to The change in velocity is due to this acceleration.this acceleration.•vvxx = = vv00 + + aaxx tt • = = vv00 + ( + (F t F t / / m)m) cos cos •vvyy = = aayy tt = ( = (F t F t / / m)m) sin sin The final velocity is The final velocity is •vvxx = 5200 m/s = 5.2 km/s = 5200 m/s = 5.2 km/s •vvyy = 260 m/s = 0.26 km/s. = 260 m/s = 0.26
View Full Document
Unlocking...