Phy 9 reviewer Q4

• Momentum


  A term that is usually used in sports to refer to a team that keeps moving and is hard to stop
• If an object doesn't move, then it has no momentum
• Interpretation of momentum formula

  Mass multiplied by velocity is equal to momentum
• Impulse


  The ability of another object's force to change the momentum of a moving object

  The product of the force exerted on a body and the time during which the force acts
• Interpretation of impulse formula

  Force multiplied by time is equal to impulse
• An egg doesn't break when dropped on grass because the grass is softer than concrete. From this, we can conclude that the egg experiences a larger impact force when dropped on concrete.
• Law of Conservation of Momentum

  The momentum of a system is constant if no external forces are acting on the system
• Collision


  A collision happens when two objects collide and exchange forces with each other

  There are two types of collision: elastic and inelastic
• Elastic Collision


  The total kinetic energy and the total momentum of a system are both conserved
• Inelastic Collision


  The total momentum of the system is conserved but the total kinetic energy decreases after the collision
• Projectile


  A particle moving near the Earth's surface under the influence of its weight only

  An object that is thrown or projected in the air at an angle
• Projectile Motion

  The motion of an object that is thrown or projected into the air at an angle

  It is a combination of horizontal and vertical motion

  It is determined only by the object's initial velocity and gravity

  The factors that affect an object's projectile are gravity, air resistance, initial speed, and the angle it is launched at

  When you throw a projectile into the air, it follows a curve called trajectory
• The path of a projectile is a curved path that determines the position of the projectile
• The higher the launch angle

  The higher the maximum height reached, but the shorter the range
• Horizontal Component


  • There is no external force acting on the object horizontally

  The horizontal motion of a projectile is constant
• Vertical Component

  • Nothing more than a free fall with a constant downward acceleration due to gravity

  The projectile changes its velocity and accelerates at 9.8 m/s² due to the influence of gravity

  As the projectile reaches the maximum height its vertical velocity becomes zero
• An object projected horizontally will reach the ground at the same time as an object dropped vertically because the downward force of gravity (9.8m/s/s) is always the same
• Projectiles thrown with the same speed with different projection angles will have different peaks and ranges
• The maximum range is obtained when the object is projected at 45⁰
• The time it takes to rise to its highest point is equal to the time it takes to fall from the highest point back to the original point of projection
• A projectile launched at 30⁰ will have the same range as when it is thrown at 60⁰ (the two numbers will add up to 90)
• Importance of Projectile Motion

  It is applied in sports like basketball to calculate and estimate an accurate shot/pass by throwing the ball at a perfect angle
• Energy


  The ability to do work

  There are different forms of energy: sound energy, thermal energy, and heat energy
• Potential Energy


  Conserved/stored energy

  Examples are gravity, chemical, and a stretched rubber band
• Kinetic Energy


  Energy in motion

  Examples are sound, motion, and an arrow released from a bow
• Law of Conservation of Energy and Energy Transformation

  Energy is neither created nor destroyed it is only transformed from one form to another
• Heat


  Energy that is transferred from one body to another as the result of a difference in temperature
• Heat Flow


  Heat transfer is the process of thermal energy exchange due to temperature differences

  Heat flows naturally from a hot body to a cold body
• Thermal Equilibrium


  If two objects are kept in contact long enough for their temperatures to become equal
• Heat transfers from higher temperature to lower temperature
• Conservation of Mechanical Energy


  Energy can neither be generated nor destroyed. It is always conserved

  The sum of the potential energy and kinetic energy at any position in a closed system will always remain the same
• Energy Transformation

  • A lamp changes electrical energy to radiant and heat energy

  A tree changes radiant energy to chemical energy
• Heat Pump


  A device that allows heat to transfer from a cold reservoir to a warmer one

  Mechanical work should be applied so that heat could be transformed
• How a Heat Pump Works

  Heat/cold energy is absorbed outside by a warm/cool liquid refrigerant

  2. The heat/cold is turned into a cold/hot gas

  3. Then, pressure is applied to the hot/cold gas turning it into cold/hot gas

  4. Lastly, the hot/cold gas is cooled/heated in the indoor unit
• If the air outside is cold, the heat pump will turn it into hot air

  If the air outside is hot, the heat pump will turn it into cold air
• Geothermal Power Plants


  They can greatly help in meeting the demand for growing energy demand every year by providing carbon-free heat

  They use steam to produce electricity
• How Geothermal Power Plants Work

  Hot water is pumped from deep underground and turned into steam

  2. The steam spins a turbine which is connected to a generator

  3. The turbine turns the generator which produces electricity

  4. The electricity is exported to the grid

  5. The cooled steam condenses back to water and is pumped/injected into the Earth to begin the process
• Electricity


  A form of energy resulting from the existence of charged particles
• How Electricity Works


  Power plants generate electricity through generators by using wind, water, coal, or natural gas

  2. Transformers increase the voltage to send electricity to long distances

  3. Then, it is passed through transmission lines to carry electricity throughout the country

  4. It reaches the neighborhood's transformers to lower the electricity voltage

  5. Electricity is distributed through distribution lines connected to your household

  6. Lastly, transformers on poles step down electricity before it enters the house