Forces - motion, resultant forces and braking Flashcards
What happens when two objects interact?
the forces they exert on each other are equal and opposite
What is the resultant force?
a number of forces acting at a point may be replaced by a single force
the single force has the same effect on motion as the original forces all acting together
the single force is the resultant force
the resultant force acting on an object may cause a change in its state of rest or motion
What effect does the resultant force acting on a stationary object have?
if the resultant force is 0, the object will remain stationary
if the resultant force is not 0, the object will accelerate in the direction of the resultant force
What effect does the resultant force acting on a moving object have?
if the resultant force is 0, the object will continue to move at the same speed, in the same direction
if the resultant force is not 0, the object will accelerate in the direction of the resultant force
What does the gradient of a distance-time graph represent?
speed
What is the velocity of an object?
speed in a given direction
What does the gradient of a velocity-time graph represent?
acceleration
additional guidance:
accelerate is in metres per second squared, m/s^2
What are the forces acting on a car travelling at a steady speed?
the resistive forces balance the driving force
When does braking force increase?
the greater the top speed of a vehicle the greater the braking force need to stop it in a certain distance
What is the stopping distance of a vehicle and what increases it?
stopping distance = drivers reaction time + distance it travels under the braking force
reaction time is affected by tiredness, drugs and alcohol
braking time is affected by weather conditions, road surface and poor tyres or brakes
How do brakes work?
friction between the brakes and the wheel reduce the kinetic energy of the vehicle
this causes the temperature of the brakes to increase
How does a vehicles shape affect its top speed?
a car that has an aerodynamic shape will travel faster due to low air resistance
