P2.2 Forces Flashcards
What is a force?
A force is a push or a pull that can change the shape of an object or change its motion or its state of rest
What is force measure in?
The unit of force is the newton (N)
What happens when two objects interact? (Newton’s third law)
They will always exert equal and opposite forces on each other (for every action, there is an equal and opposite reaction)
What is a resultant force?
A single force that has the same effect as all the forces acting on an object / the overall force
What happens if the resultant force is:
1. Zero
2. Not zero
(Newton’s first law)
Zero: the object stays at rest or at constant velocity
Not zero: the velocity of the object will change
What is the resultant force when the forces are acting in the same direction?
The sum of the forces
What is the resultant force when forces are acting in different directions?
The difference between the forces
The bigger the resultant force on an object is …
acceleration
… the greater its acceleration is
The greater the mass of an object is …
acceleration
… the smaller its acceleration is (for a given force)
What is the equation for force (resultant force)?
(resultant) Force(N) = mass(kg) x acceleration(m/s/s)
In a car what are the opposing forces to the driving force?
friction and air resistance
What is the stopping distance?
the minimum distance that a car can safely stop in
What is breaking distance?
the distance travelled by the vehicle during the time the breaking force acts
What is thinking distance?
the distance travelled by the vehicle in the time is takes the driver to react
What is the equation for stopping distance?
stopping distance=thinking distance+breaking distance
What are the factors that will affect breaking distance?
speed, weather, road conditions (all due to friction)
What are the factors that will affect thinking distance?
alcohol, tiredness/fatigue, speed, distraction, medications, reaction time
What is weight and its unit?
the weight of an object is the force of gravity on it - Newtons (N)
What is mass and its unit?
the mass of an object is the quantity of mater in it - Kilograms (kg)
What is the equation for weight?
Weight(N) = mass(kg) x gravitational field strength(N/kg)
What is the terminal velocity of a falling object?
the velocity it reaches when it is falling in a fluid, the weight is then equal to the drag force
What is extension?
length when stretched - its original length
What is Hooke’s law (for elastic behavior)?
F=ke
Force(N)=spring constant(N/m) x extension(m)
What is the spring constant (from Hooke’s law)?
the spring constant of a spring is the force per unit of extension needed to stretch it
What can be said about the extension of an object and the force applied to it?
They are directly proportional, provided that the limit of proportionality is not exceeded
How can fuel economy of road vehicles be improved?
reducing the speed
fitting a wind deflector
What are anti-skid surfaces?
Anti-skid surfaces increase the friction between a car tyre and the road surface. This reduces skids, or even prevents skids altogether.
