18 Ch 6A Linear-momentum - West Virginia University
“It isn't the mountains ahead to climb that wear you out; it's the pebble in your shoe.”- Muhammad AliPain and CollisionsMomentum, Impulse, and PressureExtra Practice Problems: 5.1, 5.7, 5.9, 5.11,5.13, 5.15, 5.17, 9.3, Conceptual 9.1TodayMomentum ( p ).(mass times velocity)Impulse ( I ).(change in momentum)Pressure ( P ).(force over some area of space)MomentumThink of a time when you’ve heard this term.(Linear) MomentumMass times Velocity.p mvSI units:kg msDirection of momentum issame as direction of velocity!
(Linear) MomentumMass times Velocity.p mvSI units:kg ms p 12 kg m/s p 0 kg m/sLet’s try itA pitcher claims he can throw a 0.145 kgbaseball with as much momentum as a 3.00 gbullet moving with a speed of 1500 m/s!What must the baseball’s speed be if thepitcher’s claim is valid?Which has greater kinetic energy?p mv1KE 2 mv2A. the ballB. the bulletC. they are the sameQ51ImpulseChange in Momentum.I Δp mvf mviSI units:kg msImpulseAre impulses bad if acted on too quickly?(Usually !)
Newton’s Second Law RevisitedFnet maFnet ΔpΔtThis is the general form of Newton’s 2nd Law.ImpulseCan also be written as average/constant force (F) on anobject times the duration of that force, ΔtFnet Δt mvf mviTime is the collision time (start to end of impact).Direction of impulse is the same as the direction ofthe force acting on an object (note: impulse onlyhappens if there’s a force!).ImpulseImpulses hurt if acted on too quickly!Fnet Δt mvf mviRemember “childfalling out of bed”example!IImpulseImpulses hurt if acted on too quickly!Fnet Δt mvf mviΔtFFΔt“Rolling with the punches”Boxers opt for more Δt rather than more force!
IFood generates the lady’s impulse.IThe wall generates the car’s impulse.A 100-g lump of clay hits a wall at 70 cm/s and sticks.A 100-g rubber ball hits the same wall at 60 cm/s andrebounds with a speed of 30 cm/s.Which object has a larger impulse magnitudedelivered by the wall during the collision?A. The clayB. The ballC.Both impulses are the same.D.Cannot be determined.Q52Impulse and Average ForceWhat if the force isn’t constant?Force vs time in a car crashHigh chance of deathabove this lineA.B.C.D.Where is the biggestimpulse?Between 70 and 80 msBetween 10 and 20 msBetween 100 and 110 msBefore the collisionQ53Impulse and Average ForceA car is travelling at 27 m/s (60 mph) and crashes into a pole,coming to rest in time 150ms. What is the average force exertedon a 100kg person strapped into the car in this collision?Favg Δt mvf mviHigh chance ofdeath abovethis lineAlways wearseatbelts!
PressureForce over Area.Which hurts more?Damage depends more on pressure than force!PressureForce over Area.Pressure or Stress F / ASI units: Pascal (Pa)Nm2Pressure (mainly for liquids and gases) orStress (for solids) tells you over what areathe force is spread.Man on a ChairA man sits on a four-legged chair with hisfeet off the floor. The combined mass of theman and chair is 95 kg. If the chair legs arecircular and have a radius of 0.50 cm at thebottom, what pressure does each leg exerton the floor?What could youdo to reducepressure andchance ofscratching?Car TiresThe four tires of an automobile are inflated to a gaugepressure of 2.0 x 105 Pa. Each tire has an area of0.024 m2 in contact with the ground. Determine theweight of the automobile.P F/A0.024 m2
Momentum ( p ).(mass times velocity)p mvImpulse ( I ).(change in momentum)I Fnet Δt mvf mviPressure ( P ).(force over some area of space)Pressure or Stress F / A
Pain and Collisions Momentum, Impulse, and Pressure "It isn't the mountains ahead to climb that wear you out; it's the pebble in your shoe." - Muhammad Ali Today Momentum ( p ). (mass times velocity) Impulse ( I). (change in momentum) Pressure ( P). (force over some area of space) Momentum Think of a time when you've heard this term.
1. Impulse and Momentum: You should understand impulse and linear momentum so you can: a. Relate mass, velocity, and linear momentum for a moving body, and calculate the total linear momentum of a system of bodies. Just use the good old momentum equation. b. Relate impulse to the change in linear momentum and the average force acting on a body.
momentum is kg·m/s. Linear Momentum Linear momentum is defined as the product of a system's mass multiplied by its velocity: p mv. (8.2) Example 8.1Calculating Momentum: A Football Player and a Football (a) Calculate the momentum of a 110-kg football player running at 8.00 m/s. (b) Compare the player's momentum with the
CHAPTER 3 MOMENTUM AND IMPULSE prepared by Yew Sze Ling@Fiona, KML 2 3.1 Momentum and Impulse Momentum The linear momentum (or "momentum" for short) of an object is defined as the product of its mass and its velocity. p mv & & SI unit of momentum: kgms-1 or Ns Momentum is vector quantity that has the same direction as the velocity.
Linear Momentum Linear momentum is defined as the product of an object's mass and velocity: p mv Units of momentum:s kg m The greater the linear momentum of a body , the greater its tendency to continue in motion. v m An iron shot (m larger) is harder to stop than a baseball (m small) of the same velocity. Momentum is a VECTOR !
Linear momentum is always conserved for an isolated system. Of course, we deal with components ix fx iy fy p p and p p I like to say that momentum is conserved in collisions and explosions. Note: The total momentum of the system is conserved. The momentum of an individual particle can change. Problem 18.
p Linear momentum of a particle of mass and velocity The Linear Momentum SI unit for li is defined as neal momentum: is the kg.m/s pmv p mv pmv The time rate of change of the linear momentum of a particle is equal to the magnitude of net force acting on th Below we will prove the fol e particle and has the direc lowing statem tion of the f ent .
4. Impulse - Momentum 3. This area is called Impulse F.dt r. 5/14/2008 Momentum - 1 25 Force, Time and Momentum The area under the force-time graph equals the change in linear momentum. If the LHS of this . Collisions - Linear Momentum is always conserved Is the collision force gravity or springs? - If YES, then Kinetic .
The linear momentum (or "momentum" for short) of an object is defined as the product of its mass and its velocity. Momentum (plural is momenta—from Latin) is represented by the symbol If we let m represent the mass of an object and represent its velocity, then its momentum is defined as (7;1) Velocity is a vector, so momentum too is a vector.
