P10 Flashcards
What is inertia
The tendency of objects to continue in their state of rest or of uniform motion is called inertia
What is newton’s first law
If the resultant force acting on an object is zero and:
The object is stationary, the object remains stationary
The object is moving, the object continues to move at the same speed and in the same direction. So the object continues to move at the same velocity
What is newtons second law
The acceleration of an object is proportional to the resultant force acting on the object, and inversely proportional to the mass of the object.
Newtons 3rd law
Whenever two objects interact, the forces they exert on each other are equal and opposite
What js the stopping distance
The stopping distance of a vehicle is the sum of the distance the vehicle travels during the driver’s reaction time (thinking distance) and the distance it travels under the braking force (braking distance).
For a given braking force the greater the speed of the vehicle, the greater the stopping distance
What is the reaction time for typical person
values range from 0.2 s to 0.9 s
How can a drivers reaction time be affected
A driver’s reaction time can be affected by tiredness, drugs and alcohol. Distractions may also affect a driver’s ability to react
How can the braking distance of a vehicle be affected
The braking distance of a vehicle can be affected by adverse road and weather conditions and poor condition of the vehicle
Adverse road conditions include wet or icy conditions.
Poor condition of the vehicle is limited to the vehicle’s brakes or tyres
What happens to the energy of a vehicle when a force is applied to the brakes
When a force is applied to the brakes of a vehicle, work done by the friction force between the brakes and the wheel reduces the kinetic energy of the vehicle and the temperature of the brakes increases
Hiw does speed affect braking force
The greater the speed of a vehicle the greater the braking force needed to stop the vehicle in a certain distance
How is deceleration inceased and what can it lead to
The greater the braking force the greater the deceleration of the vehicle. Large decelerations may lead to brakes overheating and/or loss of control
What is the equation for momentum
momentum = mass × velocit y p = mv
How does momentum change after an event
In a closed system, the total momentum before an event is equal to the total momentum after the event
This is called conservation of momentum
What is the equation for a force that is acting on a moving object
F = change in momentum/ time
F = mv - mu/ t
Force equals the rate of change in momentum
How do safety features in cars work
E.g air bags, seat belts, crash helmets
Prolong impact time so decreases the rate of change in momentum