Physics WJEC GCSE Unit 2

• Q: What is the relationship between speed, distance and time?

  Distance = speed x time
• Q: What is velocity?

  A: Speed in a given direction.
• Q: What is acceleration?

  A: The rate that an object's speed is increasing.
• Q: What is the relationship between acceleration, velocity change, and time?

  A: Velocity change = acceleration x time
• Q: How can distance travelled be calculated from a velocity-time graph?

  A: It is the area under a graph.
• Q: What is total stopping distance?

  A: The distance between a driver seeing a stimulus and the car coming to a stop. (Braking distance + thinking distance)
• Q: What is thinking distance?

  A: The time between when a driver sees something and when the driver presses the brake.
• Q: What is Braking distance?


  A: The time a car takes to stop once the brake has been pressed.
• Q: What factors affect thinking distance?

  A: Velocity of car, reaction time(tiredness/alcohol/drugs/old age), if driver is distracted.
• Q: What factors affect Braking distance?

  A: Velocity of car, mass of car, brake condition, tyre condition, road condition, weather.
• Q: What are the two ways of reducing force on occupants during collision?

  A: Reducing the speed of the collision, increasing the time for a collision.
• Q: Give examples of safety features in modern cars.

  A: Seat belts, air bags, crumple zones.
• Q:How do seat belts, air bags and crumple zones reduce the force on occupants during a collision.

  A: They increase the time of a collision by allowing themselves to be (slowly) deformed during a collision.
• Q: What are the ways that car speed is restricted?

  A: Speed limit, Speed bumps.
• Q: What is inertia?

  A: The opposition of an object to a change in its motion (or rest).
• Q: What dictates how easy it is to change an object's motion, and what is this property called?

  A: Mass, inertia.
• Q: What is Newton's first law?

  A: 'An object at rest stays at rest or an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force' (an object maintains its velocity unless acted upon by an unbalanced force).
• Q: If forces acting on it are balanced, what will an object do?

  A: Continue moving (or not) at the same velocity.
• Q: If forces acting on it are unbalanced what will an object do?

  A: Accelerate in the direction the strongest force is acting.
• Q: What equation is Newton's second law summarised as?

  A: Acceleration = resultant force/mass.
• Q: If a car has its engine on, why will it not accelerate forever?

  A: The car will accelerate until the increasing air resistance acting on it will make the forces balanced. Then it will move at a constant speed.
• Q: What is the difference between weight and mass?

  A: Mass is a measure of the matter in an object, while weight is how much force it exerts on whatever is under it, it is dependent on gravitational field strength.
• Q: What is the relationship between weight, mass and gravitational field strength?

  A: Weight = mass x gravitational field strength.
• Q: What is the gravitational field strength of earth?


  A: 10 N/Kg
• Q: What is Newton's third law?

  A: 'For every action force, there is an equal and opposite reaction force'.
• Q: If rugby players push on a scrum machine with a force of 5N, what is the reaction force of that?


  A: The machine pushes on them with a force of 5N.
• Q: What are three things that must be considered when using Newton's third law?

  A: Forces act on a different object, forces are equal in size and opposite in direction, forces are the same type(e.g.- gravitational/contact/electrical/magnetic).
• Q: What is work?

  A: A measure of the energy transferred from one object to another.
• Q: What is the relationship been force, distance moved in the direction of the force, and work done?

  A: Work done = force x distance moved in the direction of force.
• Q: Why may work done not equal the total energy transferred?


  A: Energy is often lost as heat to surroundings (e.g.- as air resistance or friction).
• Q: What is gravitational potential energy dependent on?


  A: Mass, gravitational field strength, height?
• Q: How can gravitational potential energy be calculated?


  A: Gravitational potential energy) = mass x gravitational field strength x change in height.
• Q: What is kinetic energy?


  A: A form of energy represented by an object moving.
• Q: How can the kinetic energy of a moving object be calculated?


  A: Kinetic energy = 1/2 x mass x velocity x velocity.
• Q: Describe the gravitational potential energy and kinetic energy in a ball which has been thrown upwards.


  A: The ball begins with lots of kinetic energy and loses this (the ball gets slower) as the gravitational potential energy increases. Then the ball begins to lose gravitational potential energy (the ball descends) and kinetic energy increases. When the ball lands energy is converted to heat, sound, or elastic potential if the bowl is bouncy.
• Q: What is the spring constant?

  A: A measure of the stiffness of a spring, smaller is more stretchy.
• Q: What is the relationship between force, spring constant, and extension.

  A: Force = Spring constant x extension.
• Q: Why is more work needed to stretch a spring than the (force = Spring constant x extension) equation indicates?

  A: The force equation means that if that force was continually applied to the spring would only ever stretch that far. In work done, energy is needed to stretch the spring to every amount of extension before.
• Q: What is a force-extension graph?


  A: A graph with force as a y axis and extension as an x axis, the line's gradient is dependent on the spring constant.
• Q: In a spring that doesn't obey F = kx (e.g.- one that you're beginning to deform), how would you calculate work needed to stretch or compress a spring to an amount?

  A: Area under a force-extension graph.