Forces And Motions: Definitions Flashcards
Acceleration due to gravity
The acceleration, g, experienced by an object travelling in free-fall. Its value at the surface of earth is 10m/s2.
Acceleration
The rate of change of velocity. It can be calculated from the gradient of a velocity-time graph
Braking distance
The distance a vehicle travels under the braking force. This can be affected by adverse road and weather conditions as well as the condition of the vehicle.
Centripetal force
The resultant force that acts towards the centre of the circular path of an object travelling with circular motion.
Conservation of momentum
The total momentum of a system before an event is always equal to the total momentum of the system after the event.
Circular motion
The motion of an object travelling in a circle. An object travelling in circular motion is always accelerating due to its continual direction change. This means that centripetal force is always required.
Displacement
A measure of how far an object moves in a given direction. It is the straight line between the starting and finishing points and is therefore a vector quantity.
Distance-time graph
A plot of how an object’s distance changes over time. The gradient of the graph at any point, equals the object’s speed at that point.
Distance
A measure of how far an objects distance changes over time. The gradient of the graph at any point, equals the objects speed at the point
Free fall
Motion under the force of gravity alone
Human reaction time
The time it takes for the brain to react to a stimulus. Typical human reaction times are in the range of 0.2-0.9 seconds
Human reaction time
The time it takes for the brain to react to a stimulus. Typical human reaction times are in the range of 0.2-0.9 seconds
Inertial mass
A measure of how hard it is to change an objects velocity. It equals to the ratio of force over acceleration.
Momentum
The product of an objects mass and velocity
Newton
The unit of force
Newton’s first law
If a stationary objects resultant force is zero, the object will remain stationary. If a moving object’s resultant force is zero, the object will continue to move at a constant velocity (same speed and direction)
Newton’s second law
An objects acceleration is directly proportional to the resultant force acting on it, and inversely proportional to the objects mass.
Newton’s third law
The forces that two objects exert on each other when they interact are equal and opposite
Resultant force
The single force that can replace all the individual forces acting on an object, and have the same effect
Scalars quantities
Quantities that only have a magnitude, not a direction
Speed
A scalar quantity that is a measure of the rate of change of distance. The average speed is calculated by dividing the distance travelled by the speed taken.
Stopping distance
The sum of the thinking distance and the braking distance
Stopping distance
The sum of the thinking distance and the braking distance
Thinking distance
The distance a vehicle travels during the drivers reaction time. This reaction time may be affected by tiredness, drugs and alcohol .
Velocity-time graph
A plot of how an object’s velocity changes over time. The gradient at any point, equals the object’s acceleration at that point. The area under the graph equals the object’s displacement.
Velocity
A vector quantity that is a measure of the rate of change of displacement. It is the speed in a given direction.
Weight
The force acting on an object due to gravity. It is equal to the product of the object’s mass and the gravitational field strength at its location. It can be measured using a Newton Meter.
