Momentum & Impulse
- 2. Impulse and Momentum Definitions: Momentum is the product of the mass and velocity of an object. Momentum is resistance to stopping, so it’s kind of inertia for moving bodies. Impulse is the product of the average force multiplied by the time interval over which it acts: the change in momentum. Hitting a baseball with a bat applies a force that changes the ball’s direction, changing its velocity and momentum.
- 3. Impulse and Momentum Units: Impulse = N•s (Newton-second) “ J” Momentum = kg•m/s “ p”
- 4. Impulse and Momentum Equations: Momentum p = mv Impulse J = Ft p = momentum, m = mass, v = velocity F = total net force applied, J = impulse
- 5. Impulse and Momentum Impulse-Momentum Theorem: FΔt = p 2 – p 1 The impulse on an object ( FΔt ) is equal to the change in momentum ( p 2 – p 1 ) that is causes. You can also find impulse using a force-time graph like the one above. The impulse would be the area under the curve.
- 6. Impulse and Momentum Momentum example problem: What is the momentum of an object with mass of 2.00kg and a velocity of 40.0m/s? p = (2.00kg)(40.0m/s) = 80.0 kg•m/s Impulse example problem: A force of 30000N is exerted for 4.00s on a 95,000kg mass. What is the impulse of the force? J = (30000N)(4s) = 120000N•s
- 7. Impulse and Momentum I-M theorem example problem: A 2200kg SUV traveling at 26m/s can be stopped in 21s by gently applying the brakes, in 5.5s in a panic stop, or in 0.22s if it hits a concrete wall. What average force is exerted on the SUV in each of these steps? (you’ll want to rearrange the theorem for this.) Gently braking F = -2.7x10 3 N Panic braking F = -1.0x10 4 N Hitting the wall F = -2.6 x 10 5 N