Newton’s Third Law: Impulse & Momentum

1. “How many horses had to die for this stupid, itchy wig?” Newton’s Third Law:Impulse & Momentum a momentous topic

2. “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica

3. Impulse Change in momentum “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica Is known as the “Impulse-Momentum” theorem, where

4. Momentum? Huh? “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica Inertia in motion** Product of mass & velocity **For subatomic-sized particles moving really, really fast (~90% of light speed), momentum is defined differently. It’s impossible to determine BOTH position and momentum at the same instant in time because of some freaky mathematics; hence, we have Heisenberg’s Uncertainty Principle.

5. “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica Heisenberg may have slept here . . . but, for relatively large objects (like molecules) that are moving fairly slowly (<0.9c), the classical definition of momentum works just fine, and is much less complicated.

6. For momentum p = mv the mass can change, = Dm*v = m*Dv the velocity can change, Or BOTH may change! Dp = mDv + Dmv “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica to change, Dp

7. These two canoeists (each of mass 60 kg) propel their canoe (30 kg) at 5 m/s towards an unseen rock on this pond. After the 0.5-s collision, the canoe moves back at 1 m/s. This canoe can withstand a force of 1500 N without puncturing. Big rock just under here What is the change in momentum of the canoe/passengers? Will the canoe break?

8. -5 m/s 1 m/s “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica Dp = mDv Dp = (150 kg)(6 m/s) Dp = 900 kg m/s

9. F = 1800 N “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica

10. “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica A 75-kg driver is traveling at 100 m/s when his car comes to a sudden stop. The driver is not wearing a seatbelt. He collides with the steering column for 0.005 s. The human body can withstand about 9 times the weight of the body as impact force. Has this driver committed suicide-sans-seatbelt?

11. “For every action, there exists an equal and opposite reaction.”- Isaac Newton, Principia Mathematica A 75-kg driver is traveling at 100 m/s when his car comes to a sudden stop. The driver is wearing a seatbelt. He collides with the steering column for 1.2 s. The human body can withstand about 9 times the weight of the body as impact force. Has this driver committed suicide-sans-seatbelt? This crash occurred in Oahu; yes, the driver was wearing a seat belt AND WALKED AWAY!

12. Many mooses’ mass may be more than your Maserati’s mass. This moose’s mass is 680 kg, and it is initially moving at 9 m/s. If the collision lasts for 0.5 s, how much force is sustained by the car?

13. Water leaves a fire hose at a rate of 125 kg/s with a speed of 200 m/s and strikes a wall, which stops it. (We’re ignoring any splashing back.) What is the force exerted by the water on the wall? FYI: Fire hoses were used in the 1960’s to break up peaceful civil rights demonstrations.

14. Calculate the force exerted on a rocket, given that the propelling gases are expelled at a rate of 1000 kg/s, with a speed of 60,000 m/s (at takeoff).

16. Your assignment for next time: • pp. 83+: RQ 1-8; T&E 1,3-12,15