Energy

• What is kinetic energy?

  Kinetic energy is the energy stored in moving objects.
• Why does a stationary object like a parked car have no kinetic energy?

  A stationary object has no kinetic energy because it is not moving.
• What is the equation to calculate kinetic energy?

  Kinetic energy in joules is given by the equation: $KE =$$0.5 \times m \times v^2$.
• What units are used for mass and speed in the kinetic energy equation?

  Mass is in kilograms and speed is in meters per second.
• Is the kinetic energy equation provided in the exam?

  No, the kinetic energy equation is not provided in the exam, so it must be learned.
• What energy changes occur when a car runs on petrol?

  • Chemical energy stored in petrol
  • Chemical reaction in the engine
  • Conversion of chemical energy to kinetic energy as the car moves
• Calculate the kinetic energy of a car with a mass of 700 kg moving at a speed of 20 m/s.

  The kinetic energy is $KE =$$0.5 \times 700 \, \text{kg} \times (20 \, \text{m/s})^2 =$$140,000 \, \text{J}$.
• How do scientists convert joules into kilojoules?

  Scientists convert joules into kilojoules by dividing by 1,000.
• Calculate the kinetic energy of a cyclist and bike with a total mass of 100 kg moving at a speed of 15 m/s.

  The kinetic energy is $KE =$$0.5 \times 100 \, \text{kg} \times (15 \, \text{m/s})^2 =$$11,250 \, \text{J}$.
• If a tennis ball is traveling at 50 m/s and has a kinetic energy of 75 J, how do you calculate its mass?

  The mass can be calculated using the rearranged equation: $m =$$\frac{KE}{0.5 \times v^2}$.
• What is the mass of a tennis ball traveling at 50 m/s with a kinetic energy of 75 J?

  The mass is $m =$$\frac{75 \, \text{J}}{0.5 \times (50 \, \text{m/s})^2} =$$0.06 \, \text{kg}$.
• What should you do to prepare for questions involving kinetic energy calculations?

  • Learn the kinetic energy equation: $KE =$$0.5 \times m \times v^2$
  • Practice various kinetic energy calculation problems