Stacked Ball Drop https://www.youtube.com/watch?v=2UHS883_P60 Define momentum: resistance to give up kinetic energy, quantity of motion of a moving body measured by product of mass and velocity. Momentum will increase as mass and velocity increase Why does the top ball bounce the farthest? elastic energy of the bottom large mass ball is transferred to middle to top balls This represents Conservation of Momentum

Impulse Momentum Theory

Impulse Impulse is defined as the change in momentum Impulse (J) = Force x Time Impulse will increase as time of impact increases Ex. An airbag deploying during a car crash will increase the time of impact, increasing the impulse

Real World Examples A seatbelt stretches in a car to increase time of impact A trampoline stretches as a person jumps on it, reducing the force on the person’s bones A lacrosse net catching the ball Anything that will “cushion” or move with the object impacting it will have a higher impulse

Impulse-Momentum Theory: The equation can be written as so: J= Δp Most problems will not directly give impulse of momentum, therefore a new equation must be derived Original formulas: J=FΔt p = mΔv Depending on what is given, the following equations can be used: J= mΔv Δp= FΔt FΔt = mΔv Don’t Stress! All of these are the same equation rearranged 

Calculation Examples How much impulse is needed to stop a 10kg bowling ball moving at 6 m/s? What is given? m= 10 kg V= 6 m/s What are you looking for? J =? Which equation has all three? J= mΔv J= (10 kg) (6 m/s) J= 60 Ns

Calculation Examples F= 𝑚Δ𝑣 𝑡 A car carrying a 75-kg test dummy crashes into a wall at 25 m/s and is brought to rest in 0.1s. What is the average force exerted by the seat belt on the dummy? What is given? m=75 kg v= 25 m/s t= 0.1 s What are you looking for? F= ? What has all four? Equation Chosen: FΔt = mΔv Rearrange for F F= 𝑚Δ𝑣 𝑡 Substitute: F = (75 kg) (25 m/s)/ (0.1 s) F= (1875 k m/s)/ (0.1 s) F= 18750 N