Forces Flashcards
To revise forces for key stage 2 assessments
What is the difference between scaler and vector ?
Speed and distance are scalar : have only magnitude
Displacement and velocity are vector : have direction and magnitude
Explain what a non contact force is ?
When objects are physically separated ?
Formula for weight ?
Mass x gravitational field strength
What is the rule for gravity ( attraction ) ?
The larger the mass, the stronger the field , the greater the attraction
Definition of resultant force ?
A single force representing the sum of all forces acting on an object
Formula for work done ?
Work done = Force x distance
Explain Hooke’s law ?
The extension of an elastic object , such as a spring, is directly proportional to the force applied provided that the limit of proportionality is not exceeded.
What is the difference between distance and displacement ?
Distance = how far an object moves. Does not involve direction. ( Scaler quantity ) Displacement = includes both the distance from the start point to finish point, as well as distance travelled. ( Vector quantity )
What is the difference between speed and velocity ?
Speed = does not involve direction ( scaler ) Velocity = speed in a given direction ( vector )
What is Newtons first law ?
An object has a constant velocity unless acted on by a resultant force
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
Formula for force ?
Force = mass x acceleration ( F = ma )
What is the definition of Inertia ?
The measure of how difficult it is to change the velocity of an object. Objects will remain in their existing state of motion unless acted upon by an unbalanced force
Formula for Inertial mass ?
Inertial mass = force / acceleration = f /a
What is Newtons third law ?
Whenever two objects interact, the forces they exert on each other are equal and opposite
- Every action has an equal and opposite force
Definition of reaction time ?
Time taken for driver to react in an emergency and mov their feet from the accelerator pedal to the brake pedal
Definition of thinking distance ?
Distance travelled by vehicle during reaction time (continues to move at a constant speed in this time)
Definition of braking distance ?
Distance a vehicle travels whilst it is stopped by the brakes
How do you calculate the stopping distance ?
Thinking distance + braking distance
Factor affecting the thinking distance ?
Speed Concentration Tiredness Distractions Influence of alcohol/drugs
Factors affecting braking distance ?
Speed Poor road conditions ( icy, wet) Bald tires ( low friction ) Worn brake pads Weight ( more passengers )
Formula for momentum ?
Momentum = mass x velocity ( P = mv )
*As velocity is a vector quantity, so is momentum
Definition of Conservation of momentum ?
When two objects collide, their total momentum before the collision equals their total momentum after the collision, providing theyre in a closed system with no external forces acting upon the objects
Definition of air resistance ?
This is the force that acts against gravity on a falling object. This makes different objects fall at different rates.
