Energy Momentum Collisions Impulse Momentum l A measure

Energy Momentum, Collisions, Impulse

Momentum l. A measure of how hard it is to stop a moving object l Momentum = (MASS) (VELOCITY)

Momentum Equation p= m v Units p= mv = (kg)(meter) = second kg·m s

Momentum animations l http: //physics. weber. edu/amiri/director/M omentum. html

Momentum Example 1 What is the momentum of an orange with a mass of 0. 5 kg thrown with a velocity of 5. 0 m/s? m = 0. 5 kg v = 5. 0 m/s p = mv = (0. 5 kg)(5. 0 m/s) = 2. 5 kg·m s

Momentum Example 2 An object with a mass of 3. 0 kg is traveling at a velocity of 4. 0 m/s. What is its momentum?

More momentum examples l http: //id. mind. net/~zona/mstm/physics/m echanics/momentum/introductory. Problems /momentum. Summary 1. html

Conservation of Momentum Newton’s Third Law For every action there is an equal and opposite reaction! l To accelerate an object, we must apply force

Conservation of Momentum l Force(s) must be external l Internal forces do not apply E. g. to accelerate a car, do you push on the dashboard?

Conservation of Momentum l http: //id. mind. net/~zona/mstm/physics/m echanics/momentum/introductory. Problems /momentum. Summary 3. html

Collisions Net momentum before collision = Net momentum after the collision

Elastic Collisions l http: //id. mind. net/~zona/mstm/physics/m echanics/momentum/solvers/momentum. S olvers 1. htm

Inelastic Collisions l http: //id. mind. net/~zona/mstm/physics/m echanics/momentum/solvers/momentum. S olvers 1. htm

Impulse = force exerted over time Impulse changes momentum

Impulse Equation J = (Force) (time) J = Ft = m Δv = Δp = m (v 2 -v 1) = Δp (mass)(change in velocity) = change in momentum

Impulse Units J= (Newton) (seconds) J = N·s l Force is in Newtons l Time is in seconds

Impulse Example An 8 N force acts on a 5 kg object for 3 seconds. If the initial velocity of the object was 25 m/s, what is its final velocity? F= 8 N m= 5 kg t= 3 s v 1 = 25 m/s v 2 = ? J = Ft =(8 N)(3 s) = 24 N·s BUT we need to find v 2 ………

Impulse Example J = mΔv = m (v 2 -v 1) = 24 N·s = 5 kg(v 2 - 25 m/s) = 24 = 5 v 2 - 125 m/s = 125+24= 5 v 2 = 149/5 = v 2 = 29. 8 m/s

Impulse problems l http: //id. mind. net/~zona/mstm/physics/m echanics/momentum/introductory. Problems /momentum. Summary 2. html