Momentum & Impulse Seo Physics

Objectives To understand how impact is given onto an object(s) To find the relationship between Force, mass, velocity and time To introduce conservation theory

Arresto Momentum !! (kg* m/s = kg * m/s) What is Momentum? The amount of motion created with Object’s certain mass and velocity Momentum is denoted in small letter p (Units in kg*m/s) Equation? p= m*v ; (Momentum = mass * velocity) (kg* m/s = kg * m/s) Vector quantity Both magnitude and direction

Practice What is the momentum of a fly that is 10 grams and flies at 2 m/s? 10g=.01kg p=m*v=.01x2= (0.02kg*m/s) What is the momentum of a turtle that is 1kg and moves at .05m/s? p=m*v=1x.05= (0.05kg*m/s) The turtle has more momentum (larger magnitude).

DIY What is the momentum of a truck that is 2500 kg and speeds at 9 m/s? p=m*v=2500 kg * 9 m/s 22,500kg*m/s What is the momentum of a bulldozer that has a mass of 3210kg and moves at 7m/s? p=m*v=3210 kg * 7 m/s 22,470kg*m/s

Net Momentum What is Net Momentum? Sum of all momentum in an object Exists in 1D and 2D momentum Ex). What’s the total momentum of Object 1 and Object 2? pobject1 = (0.83kg*m/s, Left) Pobject2 = (0.32kg*m/s, Left) Momentum is a vector so we need to do vector addition pnet = Σp = p1 + p2 + … pnet = 1.15kg* m/s, Left

Momentum Crash

Impulse What is Impulse? Units? 1) J= F*t (Impulse = Force *time) 1) Change in Momentum 2) Impact caused by force and amount of time in an object Denoted as upper-case J Equations? 1) J= F*t (Impulse = Force *time) 2) Δp = mΔv Units? Newton-Seconds or N*s

J = m*(vfinal – vinitial)‏ J = 5 kg*(3m/s-5m/s)=-10kg*m/s Impulse Practice A bowling ball (5kg) moving at 5m/s bowls through a set of bowling pins. Right before the ball falls down the shoot it is going 3m/s What is the impulse the bowling pins provide to a bowling ball? J = mΔv J = m*(vfinal – vinitial)‏ J = 5 kg*(3m/s-5m/s)=-10kg*m/s

J = mΔv = m*(vfinal-vinitial) = .3*(25-0) = 7.5kg*m/s J = FΔt DIY In football, a field goal is kicked with the football initially at rest. The football 0.3 kg is kicked at 25m/s.  The player's foot was in contact with the ball for 0.1 seconds. What was the impulse on the ball? What is the average force during the time of contact? J = mΔv = m*(vfinal-vinitial) = .3*(25-0) = 7.5kg*m/s J = FΔt 7.5 = F * 0.1 F= 75 N

Impulse

Impulse-Momentum Theorem

Conservation of Momentum What does it mean to be Conserved? Matter is neither lost nor destroyed; transferred fully What is Conservation of Momentum? Equation?

What is an Elastic Collision? Collision that does not stick and repels Ex) Spring stretches then coils back Equation? m1iv1i+ m2iv2i=m1fv1f+ m2fv2f

Inelastic Collision What is an Inelastic Collision? Equation? Collision that sticks and attracts Partially Inelastic Collison Separated but not in original form Perfectly Inelastic Collision When two objects collide and stick together Equation? m1iv1i+ m2iv2i=vf (m1+m2) Ex. In Biology, combination of Nucleotides and form a double helix

Practice A 10 kg object moves at a constant velocity 2 m/s to the right and collides with a 6 kg object moving at a velocity 5 m/s to the left. What are the initial and final momentum of the system? mr = 10kg, vr = 2m/s, ml = 6kg, vl = -5m/s, p = mv pi = m1v1i + m2v2i pi = 10*2 + 6*(-5) = -10kgm/s = (10kgm/s,left)

DIY p = mv m1v1i + m2v2i = m1v1f + m2v2f Car A with a mass of 24,000 kg moves at a constant velocity of 8 m/s collides with an empty stationary car B with a mass of 10,000 kg. After the collision the car A is moving at 5 m/s in the same direction. What is the velocity of car B after the collision? m1 = 24,000kg v1i = 8m/s v1f = 5m/s m2 = 10,000kg v2i = 0m/s v2f = ? p = mv m1v1i + m2v2i = m1v1f + m2v2f 24,000*8 + 10,000*0 = 24,000*5 + 10,000*v2f v2f = 7.2 m/s

TOT Bar Charts Representational tool to visualize initial momentum, Impulse/system, and final momentum   Initial momentum Final momentum

TOT Bar Charts Practice A 8kg cart 1 moving with 10m/s to the right strikes a 10kg cart 2 that starts with 2 m/s. If the 10kg cart 2 is moving with 6m/s to the right after the collision, what is the velocity of the 8kg cart after the collision? Equation: m1v1i + m2v2i = m1v1f + m2v2f m1v1i=(8 kg*10 m/s)=80 kg*m/s m2v2i=(10 kg*2 m/s)=20 kg*m/s m1v1f=(8 kg*vf) m2v2f=(10 kg*6 m/s)=60 kg*m/s 80 kg* m/s + 20 kg* m/s = 8 kg* v + 60 kg* m/s v= 5 m/s   Initial momentum Final momentum