1.1.2 Changes in Energy

• Kinetic energy

  The energy stored in moving objects.
• What is kinetic energy measured in?

  Joules.
• Stationary objects have no kinetic energy.
• Kinetic energy = 0.5 x mass x velocity ^ 2
• What is mass measured in?

  Kilograms.
• What is speed measured in?

  Meters per second.
• Joules to kilojoules = divide by 1000
• Kilojoules to joules = multiply by 1000
• The kinetic energy of an object is the energy that it possesses due to its motion.
• Which two measurements are required to calculate the kinetic energy of an object?

  Mass and velocity.
• An object has a mass of 2 kg, and is travelling at a velocity of 5 m/s. How much kinetic energy does the object have?

  25J.
• A cyclist is riding down a hill at a speed of 10 m/s. The cyclist has 4 kJ of kinetic energy. Calculate the cyclist's mass.

  80kg.
• What is weight measured in?

  Newtons.
• What is the difference between mass and weight?

  Mass is a measure of the amount of matter in an object, while weight is the force exerted on an object due to gravity.
• The weight of an object is determined by both the strength of the gravitational field acting upon it, and the object's mass.
• What is the formula for weight?

  Weight = mass x gravity.
• What is the weight of a 70 kg object on earth? (The Earth's gravitational field strength is 9.8 N/kg)

  686N.
• A car on earth experiences a downwards weight of 8820 N, what is the mass of the car? (The Earth's gravitational field strength is 9.8 N/kg)

  900kg.
• Tony has a mass of 65 kg on Earth. What is Tony's mass on the moon?

  65kg.
• Tony's mass is 65 kg. What is his weight on Earth? (The Earth's gravitational field strength is 9.8 N/kg)

  637N.
• Tony’s mass is 65kg. What is his weight on the moon? (The moon's gravitational field strength is 1.6 N/kg)

  104N.
• Every object in the universe exerts a force of gravitational attraction on every other object in the universe. Which two factors determine the strength of the gravitational force of attraction?

  Mass and distance.
• What is gravitational potential energy measured in?

  Joules.
• The value of the gravitational field strength on the Earth's surface is ____ N/kg:

  9.8.
• Gravitational potential energy = mass x gravitational field strength x height
• Tony, who has a mass of 65 kg, climbed the stairs from the ground floor, up to the fourth floor, which is 20 m higher. How much gravitational potential energy did Tony gain? (The Earth's gravitational field strength is 9.8 N/kg)

  12,740J.
• Freya, who has a mass of 60 kg, jumps from a boat into the sea. Just before she hits the water, she has lost 1,470 J of gravitational potential energy. How far did she fall?

  2.5m.
• Is weight or mass a force?

  Weight.
• Elastic potential energy = 0.5 x spring constant x extension²
• What is elastic potential energy measured in?

  Joules.
• What is spring constant measured in?

  Newtons per meter (N/m).
• What is extension measured in?

  Meters.