P5: Forces [𝐇𝐢𝐠𝐡𝐞𝐫 𝐏𝐚𝐩𝐞𝐫 𝟐]

• What is the law of conservation of momentum?

  In a closed system, the total momentum before an event is equal to the total momentum after the event
• What is the unit for momentum?

  kg m/s
• What equation is used to find an object's momentum?

  momentum = mass x velocity
• What is momentum?


  A vector quantity which is the product of both an object's mass and velocity - it can be defined as "mass in motion".
• Why is applying the brake too hard/quickly dangerous?

  Very large decelerations may cause brakes to overheat or loss of control of the vehicle
• What happens to energy stores when a vehicle's brakes are applied?

  Work is done by the friction force between the brakes and the wheel which reduces the kinetic energy of the vehicle and increases the thermal store (temperature) of the brakes
• What factors affect braking distance?

  poor road conditions (wet or icy), poor weather conditions, poor condition of the vehicle (brakes or tyres)
• What factors affect a driver's reaction time?

  Tiredness, drugs, alcohol and distractions.
• What is a typical human reaction time?

  0.2 - 0.9 seconds
• What is stopping distance?

  the distance a vehicle travels during the driver thinking and the driver braking
• What is Newton's 3rd law?

  Whenever two objects interact, the forces they exert on each other are equal and opposite.
• What does the symbol ~ mean?

  approximately
• How would you find an object's inertial mass?

  m = F/a (inertial mass is the ratio of force over acceleration)
• What does an object's inertial mass measure?

  How difficult it is to change the object's velocity.
• What is Newton's 2nd law?

  An object's acceleration is directly proportional to the resultant force acting on it, and inversely proportional to its mass
• What is inertia?

  The tendency for objects to continue in their state of rest or in uniform motion (like in Newton's first law)
• What is Newton's 1st law?

  If the resultant force on an object is zero, its motion does not change
• How do objects reach terminal velocity?

  An object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity.
• How can you find the displacement of an object from a velocity-time graph?


  by finding the area under the line of the graph
• How can you find the acceleration of an object from a velocity-time graph?

  by calculating the gradient
• What does 'decelerating' mean?

  an object is changing its speed by slowing down
• What equation is used to calculate acceleration?

  acceleration = change in velocity ÷ time
• What is acceleration?

  how quickly an object changes its velocity
• How can you find the speed of an object from a distance-time graph?

  calculating the gradient
• Descrive the speed and velocity of an object travelling in a circle

  motion in a circle involves constant speed but changing velocity
• What is an average value for the speed of sound in air?

  around 330 m/s
• What is an average human cycling speed?

  around 6 m/s
• What is an average human running speed?

  around 3 m/s
• What is an average human walking speed?

  around 1.5 m/s
• What is the difference between speed and velocity?

  Speed is how fast something moves. Speed does not involve direction. Speed is a scalar quantity.

  The velocity of an object is its speed in a given direction. Velocity is a vector quantity.
• What is velocity?

  Speed in a given direction.
• What is the difference between distance and displacement?

  Distance is how far an object moves. Distance does not involve direction. Distance is a scalar quantity.

  Displacement includes both the distance an object moves, measured in a straight line from the start point to the finish point and the direction of that straight line. Displacement is a vector quantity.
• What equation is used to find the force applied to a spring when stretching/compressing it?

  F = spring constant x extension
• What is meant by the limit of proportionality (in the context of springs)?

  The point where a spring's extension stops being proportional to the force applied to it. A plotted graph would become non-linear at this point.
• What is inelastic deformation?


  Where an object doesn't return to its original shape after the force deforming it is removed.
• What is elastic deformation?


  Where an object returns to its original shape after the force deforming it is removed.
• What energy store increases when work is done against friction?

  thermal store (the object's temperature increases)
• What unit is equivalent to 1 newton-metre?

  1 Joule
• What equation can be used to find work done?


  Work done = force x distance
• What is 'work done'?

  the energy transferred to an object by a force