physics

• average speed =


  distance / time

  v = d / t
• Standard Unit for mass (m)

  kilogram

  (kg)
• Standard Unit for distance (d) or displacement (s)


  metre

  (m)
• Standard Unit for speed (s) or velocity (v)

  metre/second

  (m/s)
• Standard Unit for acceleration (a)


  metre/second²

  (m/s²)
• Standard Unit for Force (F)

  Newton

  (N)
• Standard Unit for time (t)

  Second

  (s)
• Standard Unit for gravitational field strength (g)


  Newton/kilogram

  (N/kg)
• Standard Unit for moment

  (Paper 2 Only)

  Newton metre

  (Nm)
• Standard Unit for momentum (p)

  (Paper 2 Only)

  kilogram metre/second

  (kg m/s)
• What does the gradient of a distance-time graph represent?

  Gradient or the slope gives the speed.

  Flat line means stationary, straight line means constant speed, curved line means accelerating

  
• Describe how to investigate the motion of a toy car

  - Set a ramp up so that the top of it is a certain height, h, above the desk, and the other end is fixed in place on the desk.

  - Measure the distance the toy car will travel down the ramp using a metre ruler.

  - Measure the time taken for the toy car to roll down the ramp using a stop watch.

  - As it is difficult to start and stop the watch at exactly the right time, the experiment is repeated five times so an average time can be calculated.

  - Divide the distance by the average time to calculate the average speed of the car.

  - To improve the accuracy of the experiment, light gates connected to electronic timers could be used as human reaction times will no longer affect the results. We still take multiple readings as the car may not have been released in exactly the same way each time.

  - An electronic timer that reads to more decimal places will give the answer to a greater level of precision.
• Acceleration =


  Change in velocity/time taken

  a = (v-u) / t
• What does the gradient of a velocity-time graph represent?

  What does the area underneath the line represent?

  gradient = acceleration

  flat line = constant velocity

  straight lines = constant acceleration (changing velocity)

  area under graph = distance travelled

  
• (final speed)² =


  (initial speed)² + (2 x acceleration x distance)

  v² = u² + (2 x a x s)

  (This equation is given to you)
• A force can change an objects....

  - speed

  - shape

  - direction
• Types of force....


  Gravitational (Weight)

  Electrostatic

  Magnetic

  Friction

  Air Resistance (Drag)

  Upthrust (from fluids)

  Reaction (from solids)

  Engine force

  (and more...)
• What is Scalar?

  Give some examples

  A measurement with just magnitude.

  Time, distance, temperature, mass, energy, charge, area, volume, frequency etc.
• What is a Vector?

  Give some examples

  A measurement with magnitude and direction.

  Velocity, acceleration, force, weight, momentum, etc.
• There is an unbalanced force


  when 2 or more forces acting on an object are uneven
• Resultant Force is.....


  The combination of all forces acting on an object.

  
• Newton's 2nd Law: Force =


  mass x acceleration

  F = m x a
• Newton's 2nd Law: Acceleration


  force / mass

  a = F / m
• Newton's 2nd law: Mass


  force / acceleration

  m = F / a
• Weight =


  mass x gravitational field strength

  W = m x g
• Friction and Air Resistance act in what direction?

  The direction that opposes motion (e.g. if an object is falling then air resistance is acting upwards)
• Stopping Distance =


  Thinking Distance + Braking Distance.

  It is the total distance for the car to come to a complete stop
• What is Thinking Distance? What factors affect it?


  The distance taken for the driver to react and apply the brakes.

  - Tiredness, Alcohol or drugs, Distractions, Age, Poor Visibility (e.g. fog), Reaction Time
• What is Braking Distance? What factors affect it?

  The distance traveled while the braking force stops the car.

  - Speed, Condition of the tires and brakes, Condition of the road surface (including weather conditions such as ice or water on the road), Mass of the vehicle
• What is Terminal Velocity? What is the Resultant force on an object traveling at Terminal Velocity? What forces are acting on an object falling at Terminal Velocity?

  Where an object reaches a maximum constant velocity. The forces on the object are balanced and so the resultant force is Zero Newtons.

  As an object falls, its weight causes it to accelerate. As it gets faster, the air resistance increases until it balances the weight of the object. At this point the forces are balanced and it no longer accelerates.
• Describe how to investigate how the extension of an object, such as a spring, varies with applied force.

  - Clamp a spring onto a stand, such that it is hanging vertically down.

  - Measure the spring's original length.

  - Place a known weight (100g = 1N) on to the end of the spring and measure how far it has extended. A pointer attached to the spring (fiducial marker) can help to reduce parallax errors.

  - Repeat the process by adding one weight at a time and measuring the extended length each time.

  - Calculate the extension for each weight (Extension = extended length - original length)

  - Plot a graph of force against extension

  - Draw a line of best fit. It should be a straight line through the origin. If it is, then the extension is proportional to the applied force, and the spring is said to obey Hooke's law.

  - The Spring Constant can be calculated by dividing the change in Force by the extension.

  
• Hooke's law says...


  the extension of a spring (or other material) is proportional to the force applied to it
• What is elastic behaviour?


  The ability of a material to recover its original shape after the forces causing deformation have been removed.
• What is the Conservation of Momentum?

  (Paper 2 only)

  The total momentum of objects before a collision is equal to the total momentum of objects after the collision.
• Momentum =

  (Paper 2 only)


  mass x velocity

  p = m x v
• Car safety features....

  (Paper 2 Only)

  crumple zones, seat belts and airbags increase

  the time taken for momentum to reach 0, and therefore reduce the force exerted on the passenger.
• Relationship between Force, change in momentum, and time taken.

  (Paper 2 Only)

  Force = change in momentum / time taken

  F = (m x v - m x u) / t

  (this equation is given to you)
• Newton's Third Law...

  (Paper 2 Only)

  For every action force there is an equal and opposite reaction force.

  (If you push on something, it pushes back on you with the same amount of force in the opposite direction)

  
• What is a moment?

  (Paper 2 only)

  The turning effect of a force around a fixed point called a pivot.
• Moment (Nm) =

  (Paper 2 only)


  force x perpendicular distance from the pivot