Energy

• What are the different energy stores mentioned?

  Magnetic, chemical, kinetic, elastic potential, thermal, gravitational, electrical, nuclear
• In how many ways can energy be transferred?

  Four ways: mechanical, electrical, heating, radiation
• What is the formula for work done?

  • Work Done = Force x Distance
  • Work is measured in Joules
  • Force is measured in Newtons
  • Distance is measured in Metres
• What is the definition of work in physics?

  Work is the process of transferring energy
• What is the unit of power?

  Watts
• What is the formula for power?

  Power = Work Done / Time Taken
• How much work is done by a boom lift lifting a 900N man to a height of 5m?

  4500J
• What is the power of an electric motor that does 600J of work every minute?

  10W
• What is efficiency in terms of energy transfer?

  • Efficiency = Useful Energy Output / Total Energy Input
  • Can be expressed as a percentage by multiplying by 100%
  • No units for efficiency
  • Cannot exceed 1 (or 100%)
• What is the formula for kinetic energy?

  Kinetic Energy = ½ x Mass x Velocity²
• What is the unit of kinetic energy?

  Joules
• What does gravitational potential energy depend on?

  Height above the ground
• What is the formula for gravitational potential energy?

  Gravitational Potential Energy = Mass x g x Height
• What is the value of g on Earth?

  1. 8 N/kg
• What happens to the energy of a pendulum as it swings?

  • At the highest position: maximum GPE, no KE
  • As it drops: loses GPE, gains KE
  • At the bottom: maximum KE, GPE is zero
  • Total energy remains constant
• What is the principle of energy conservation in a pendulum?

  • No energy is lost to heat, sound, etc.
  • GPE at the top converts to KE at the bottom
  • Formula: E_p = E_x
• How can materials be described based on their response to forces?

  • Stiff, ductile, strong, weak, brittle
  • Elastic (returns to original shape) vs. plastic (does not return)
• What is Hooke's Law?

  The extension of a spring is directly proportional to the force applied to it
• What is the formula for Hooke's Law?

  Force = Spring Constant x Extension
• What is the unit of spring constant?

  N/m
• What happens when a spring is overstretched?

  • Hooke's Law is no longer obeyed
  • The graph starts to curve
  • The spring will not return to its original shape
• What are the SUVAT equations used for?

  • Describe motion of an object with constant acceleration
  • Variables: s (displacement), u (initial velocity), v (final velocity), a (acceleration), t (time)
• What does 's' represent in the SUVAT equations?

  Displacement
• What does 'u' represent in the SUVAT equations?

  Initial velocity
• What does 'v' represent in the SUVAT equations?

  Final velocity
• What does 'a' represent in the SUVAT equations?

  Acceleration
• What does 't' represent in the SUVAT equations?

  Time
• What is the significance of the gradient in a velocity-time graph?

  • The gradient represents acceleration
  • Area under the graph represents displacement
• What is the value for acceleration due to gravity?

  1. 8 m/s²
• What happens to the speed of an object at its highest position when thrown upwards?

  The speed is 0 m/s
• What is the relationship between ascent and descent time for an object thrown upwards?

  • The ascent and descent times are equal
  • Total time of flight is twice the ascent time
• What is the resultant force?

  A single force that has the same effect as the separate forces combined
• How can free body diagrams help in physics?

  • Simplify force diagrams
  • Show direction of resultant force
  • Help analyze motion of objects
• What happens when two forces act at right angles to each other?

  The resultant force is found using a vector triangle
• How do you find the resultant force using Pythagoras' Theorem?

  F = √(F₁² + F₂²)
• How do you find angles using 'SOH-CAH-TOA'?

  tan θ = opposite / adjacent
• What is the process for resolving forces when more than two forces act on an object?

  • Resolve forces into one horizontal and one vertical force
  • Continue using vector addition to find resultant