Shell notes
A moving object can have a large momentum if it has a large mass, a high speed, or both.
-Momentum (p) is the mass_________ of the object multiplied by its _velocity _____________.
-A moving truck has more momentum than a car moving at the same speed because the truck has more __mass___________.
-A fast car can have more momentum than a slow truck.
-A truck at __rest_________ has no momentum at all.
The change in momentum depends on the force that acts and the length of time it acts.
-The quantity force x time interval is called__impulse ___. In short-hand notation, impulse__ = F*t.
-The greater the impulse exerted on something, the greater will be the change in momentum _________. The exact relationship is impulse = change in momentum or Ft = Δ(mv).
-To increase the momentum of an object, apply the __greatest_________ force possible for as __long_________ as possible. A golfer teeing off and a baseball player trying for a home run do both of these things when they swing as hard as possible and follow through with their swings.
-In the case of decreasing momentum, a longer contact time reduces the force_________ and decreases the resulting deceleration. A padded dashboard in a car is safer than a rigid, metal one because the padded dashboard increases the time_____ of contact.
Bouncing: The impulse required to bring an object to a stop and then to “throw it back again” is greater than the impulse required merely to bring the object to a stop.
-It takes an __impulse____ impulse to catch a flower pot and throw it back up than merely to catch it.
-A karate expert strikes the bricks in such a way that their hand is made to __bounce_________ __back_________, yielding as much as twice the impulse to the bricks.
Conservation of Momentum: The law of conservation of momentum states that, in the absence of an external force, the momentum of a system remains unchanged.
-The law of conservation of momentum describes the momentum of a system.
-If a system undergoes changes wherein all forces are internal—for example, in atomic nuclei undergoing radioactive decay, cars colliding, or stars exploding—the net momentum of the system before and after the event is the __balanced___________.
-The momentum before firing a cannon is __zero_________ . After firing, the momentum is still __zero_______ because the momentum of the cannon is equal and opposite to the momentum of the cannonball.
Collisions: Whenever objects collide in the absence of external forces, the net momentum of both objects before the collision equals the net momentum of both objects after the collision.
-When objects collide without being permanently deformed and without generating heat, the collision is said to be an __elastic_______ collision.
-Colliding objects bounce perfectly inelastic collisions.
-A collision in which the colliding objects become distorted and generate heat during the collision is an __inelastic___________ collision.
-Whenever colliding objects become tangled or couple together, a totally inelastic collision occurs.
-Perfectly elastic collisions are not common in the everyday world. At the microscopic level, however, perfectly elastic collisions are commonplace. For example, electrically charged particles bounce off one another without generating heat.
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