Forces and Braking

• What is meant by the braking distance of a vehicle?

  the distance travelled under the braking force
• What does the word accelerate mean?

  Getting faster
• Explain why the stopping distance of the car increases if the driver is very tired.

  the reaction time will increase increasing the thinking distance
• Total Stopping Distance

  The total distance required for a car to come to a complete stop, including both thinking distance and braking distance.
• Speed of the Vehicle

  The rate at which the car is traveling, which affects the stopping distance.
• Road Conditions

  The state of the surface on which the car is driving, such as dry, wet, or icy conditions, which can impact the stopping distance.
• Tire Condition

  The quality and state of the car's tires, including the tread depth and inflation pressure, which influence the stopping distance.
• Weight of the Vehicle

  The mass of the car and its contents, which affects the stopping distance.
• Thinking Distance .

  The distance traveled by the car during the driver's reaction time, which contributes to the total stopping distance
• Braking Distance

  The distance traveled by the car under the braking force, which is part of the total stopping distance.
• Relationship between

  Thinking Distance, Braking Distance, and Stopping Distance The stopping distance= thinking distance+the braking distance.
• Factors that Affect Thinking Distance

  tiredness, age, and speed
• Factors that Affect Braking Distance

  The road surface condition, including factors like icy conditions
• Why does stopping distance Increase due to drivers fatigue

  When a driver is fatigued, their reaction time increases, leading to an increase in the thinking distance and, consequently, the total stopping distance.
• Increase in Temperature of Brakes when Applying the Brakes

  When the brakes are applied, the work done by friction causes a decrease in kinetic energy and an increase in thermal energy, resulting in an increase in the temperature of the brakes.
• Form of energy Stored in a Stretched Spring

  elastic potential energy.
• Distance quantity

  Scalar quantity (no specific direction required)
• If an object moves 3 metres to the left and then 3 metres back to its initial position, the object's total displacement is zero
• Displacement

  Vector quantity (involves direction)
• A typical value for the speed of sound is 330 m/s
• A typical value for human walking speed is 1.5 m/s
• A typical value for human running speed is 3 m/s
• A typical value for human cycling speed is 6 m/s
• Distance, speed and time equation


  Distance = Speed x Time, Distance (m), Speed (m/s), Time (s)
• An object travelling at a constant speed in a circle cannot have a constant velocity because velocity is a vector quantity and the direction is continuously changing
• Calculating speed from a distance-time graph

  Speed is equal to the gradient of the graph
• Calculating speed at a given time from a distance-time graph for an accelerating object (Higher)

  1. Draw a tangent to the curve at the required time

  2. Calculate the gradient of the tangent
• Equation for average acceleration

  Acceleration = (Change in Velocity)/(Time Taken), Acceleration (m/s²), Velocity (m/s), Time (s)
• Calculating distance from a velocity-time graph (Higher)

  Distance is equal to the area under the graph
• The approximate value for the acceleration of an object in free fall under gravity near the Earth's surface is 9.8 m/s²
• When an object is falling at terminal velocity, the resultant force acting on it is zero
• Newton's first law for a stationary object


  If the resultant force on a stationary object is zero, the object will remain at rest
• Newton's first law for a moving object

  If the resultant force on a moving object is zero, the object will remain at constant velocity (same speed in same direction)
• When a car is travelling at constant velocity, the braking forces are equal to the driving forces
• If an object changes direction but remains at a constant speed

  There is a resultant force
• Inertia


  The tendency of an object to continue in its state of rest or uniform motion
• Newton's Second Law

  1. Resultant force = Mass x Acceleration

  2. F = ma
• Newton's Second Law

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

  • A measure of how difficult it is to change a given object's velocity
  • The ratio of force over acceleration
• The symbol ~ is used to represent an approximate value