Stopping Distances and Momentum

• What is the equation for stopping distance?

  stopping distance = thinking distance + braking distance
• What factors increase braking distance?

  1. Faster vehicle speed
  2. Wet or icy weather
  3. Poor road surface
  4. Damaged or worn brakes or tyres
• What is the typical stopping distance at 30 mph?

  30 m
• What is the typical stopping distance at 50 mph?

  70 m
• What is the typical stopping distance at 70 mph?

  123 m
• What is the typical stopping distance at 90 mph?

  196 m
• How does vehicle speed affect braking force?

  The faster the vehicle, the greater the braking force needed
• What can very large deceleration cause?

  Brakes to overheat and vehicle to skid
• What happens to momentum before and after an explosion?

  • Before explosion: momentum is zero
  • After explosion: momentum cancels out to zero
• How does mass affect momentum?

  The greater an object's mass, the greater its momentum
• How does velocity affect momentum?

  The greater an object's velocity, the greater its momentum
• What is the work done when stopping a vehicle?

  • Driver brakes press brake pads onto wheels
  • Friction causes work to be done
  • Energy transfers from kinetic to thermal energy
  • Brakes heat up
• What is the principle of conservation of momentum?

  • In a closed system, total momentum before an event equals total momentum after an event
• What is the formula for momentum?

  P = mv
• What does a long reaction time indicate?

  The longer the distance, the longer the reaction time
• How do distractions affect reaction time?

  Distractions affect your ability to react