Energy Stores and Changes Quiz

Energy Stores and Changes

• A system is an object or group of objects. Energy storage in a system changes as the system changes.
• Examples include: an object thrown upwards, a moving object hitting an obstacle, a constant force accelerating an object, or a car slowing down.
• Students should describe changes in energy storage in common situations.
• Calculate energy changes due to heating, work by forces, and current flow.
• Calculate how overall energy is redistributed within a system during changes.

Kinetic Energy

• Kinetic energy (Ek) of a moving object is calculated using: Ek = 0.5 × mass × (speed)²
• Ek is in joules (J)
• Mass is in kilograms (kg)
• Speed is in meters per second (m/s)

Elastic Potential Energy

• Elastic potential energy (E) stored in a stretched spring is calculated using: E = 0.5 × spring constant × (extension)²
• E is in joules (J)
• Spring constant (k) is in newtons per meter (N/m)
• Extension (e) is in meters (m)

Gravitational Potential Energy

• Gravitational potential energy (Ep) gained by an object raised above ground level is calculated using: Ep = mass × gravitational field strength (g) × height
• Ep is in joules (J)
• Mass is in kilograms (kg)
• Gravitational field strength (g) is in newtons per kilogram (N/kg).
• Height is in meters (m)

Energy Changes in Systems (Temperature Changes)

• The amount of energy stored in or released from a system as its temperature changes can be calculated using: ΔE = mcΔθ
• ΔE is the change in thermal energy in joules (J)
• m is the mass in kilograms (kg)
• c is the specific heat capacity in joules per kilogram per degree Celsius (J/kg °C)
• Δθ is the temperature change in degrees Celsius (°C)
• Specific heat capacity is the amount of energy to raise the temperature of one kilogram of a substance by one degree Celsius.

Power

• Power is the rate of energy transfer or work done.
• Power (P) = energy transferred / time
• Power (P) = work done / time
• Power is in watts (W)
• Energy/work transferred is in joules (J)
• Time is in seconds (s)

Energy Conservation and Dissipation

• Energy can be transferred, stored, or dissipated, but cannot be created or destroyed
• Only part of the energy is usefully transferred
• The rest is dissipated, stored in less useful ways ("wasted")
• Ways to reduce unwanted energy transfer include lubrication and thermal insulation.

Efficiency

• Energy efficiency is the ratio of useful output energy to total input energy.
• Efficiency = useful output energy transfer / total input energy transfer
• Efficiency = useful power output / total power input
• Units must be consistent
• Efficiency can be expressed as a decimal or a percentage.

Test your understanding of energy storage and changes within a system. This quiz covers concepts like kinetic and elastic potential energy calculations and their applications in various scenarios. Get ready to dive into energy transformations and redistributions!