Physics Review Project Dulce and Trey

Chapter Nine: Law of Conservation of Momentum

Momentum- p=mv Solving the problem: Prepare: Choose an isolated system or a system that is isolated during at least part of the problem. Draw a visual overview of the system before and after the interaction. Solve: Write the law of conservation of momentum in terms of vector components. The total momentum of an isolated system is a constant (P=P) Conservation of angular momentum: the angular momentum L of a rotating object subject to zero external torque does not change (L=L) This can be written in terms of the moment of inertia and angular velocity as I f w f =I i w i

Impulse: Is a quantity that describes the effect of a net force acting on an object ( a kind of moving force). It is also represented by the symbol J and is the product of the average net force acting on an object and its duration. J = F ̅ Δt Momentum: is a quantity that describes an object’s resistance to stopping (a kind of “moving inertia”). It is also represented by the symbol p (boldface) and is the product of an object’s mass and velocity. p = m v Impulse and momentum are related by the impulse momentum theorem p x= J x This is alternative statement of Newton’s second System- a group of interacting particles isolated system- a system on which the net external force is zero. Befor and after visual overview: Define the system Use two drawing to show the system before and after the interaction List known info and identify what you are trying to find

Applications Collisions- two or more particles come together. Explosions- two or more particles move away from each other Explosion- two or more particles move away from each other Two dimensions- both the x and y components of the total momentum P must be conserved giving two simultaneous equations.

Practice Problems Two particles collide, one of which was initially moving and the other initially at rest. a.Is it possible for both particles to be at rest after the collision? Give an example in which this happens, or explain why it happens. Both particles cannot be at rest immediately after the collision. if they were both at rest then some momentum would have to be lost to a third object that is part of the system. a.Is it possible for one particles to be at rest after the collision? Give and example in which this happens or explain why it can’t happen If the masses are equal and the collision elastic, the moving particle will stop and give all of its momentum to the previously resting particle. A good example of this appears when a billiard ball rolls directly into another resting billiard ball.

Chapter 15: The Wave Model

This model is based on the idea of a traveling wave, which is an organized disturbance traveling at a well-defined wave speed v. ●Transverse waves- the particles of the medium move perpendicular to the direction in which the wave travels ●longitudinal waves- the particles of the medium modium move parallel to the direction in which the wave travels Mechanical waves require a material medium. The speed of the wave is a property of the medium, not the wave. The speed does not depend on the size or shape of the wave ●For a wave on a string, the string is the medium ●A sound wave is a wave of compressions and rarefactions of a medium such as air. For a periodic wave, the wavelength is the distance between crests. A history graph is a graph of the displacement of one point in a medium versus time. For a periodic wave, the period T is the time between.

Sinusoidal waves are produced by a source moving with simple harmonic motion. The equation for a sinusoidal wave is a function of position and time. For a spherical wave the power decreases with the surface area of the spherical wave fronts:

Application The Doppler effect is the shift in frequency when there is relative motion of a wave source (frequency f 0, wave speed v) and an observer Moving source, stationary observer: Stationary force, moving observer:

Practice Problem A wave pulse travels along a string at a speed of 200 cm/s. What will be the speed if: a.The string’s tension is doubled? b.The string’s mass is quadrupled (but its length is unchanged)? c.The string’s length is quadrupled (but its mass is unchanged)? d.The string’s mass and length are both doubles.

The End