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Forces Topic Sheet Revision - Coggle Diagram
Forces Topic Sheet Revision
Using a free body diagram to show the magnitude and direction of the forces acting on the object
The size of the arrow in a free-body diagram reflects the magnitude of the force. The direction of the arrow shows the direction that the force is acting. Each force arrow in the diagram is labelled to indicate the exact type of force. It is generally customary in a free-body diagram to represent the object by a box and to draw the force arrow from the centre of the box outward in the direction that the force is acting.
A single force can be resolved into two components acting at right angles to each other - use Pythagoras’ theorem on forces.
The two component forces together have the same effect as the single force.
Use vector diagrams to illustrate: resolution of forces; equilibrium situations and determine the resultant of two forces including magnitude and direction - applying trigonometry to vector diagrams.
Vector diagrams can be used to resolve the pulling force into a horizontal component acting to the right, and a vertical component acting upwards.
Work done against the frictional forces acting on an object causes a rise in the temperature of the object.
In all cases of "compressing", "stretching" and "bending", two forces are involved
Elastic deformation occurs when an object returns to its original shape and size after the forces are removed. An object that does not return to its original shape after the forces have been removed has been in-elastically deformed.
Force = spring constant x extension
The amount of elastic potential energy stored in a stretched spring can be calculated using the equation:
Ee = 1/2kx2
A force that stretches (or compresses) a spring does work and elastic potential energy is stored in the spring. Provided the spring does not go past the limit of proportionality the work done on the spring and the elastic potential energy stored are equal.
Centre of mass - a point representing the mean position of the matter in a body or system.
Stability - The state of being stable
The position of the centre of gravity of an object affects its stability. The lower the centre of gravity (G) is, the more stable the object. The higher the centre of gravity the more likely an object is to topple over if it is tilted.
The atmosphere is a thin layer of air round the Earth. The atmosphere gets less dense with increasing altitude.
Air molecules colliding with a surface create atmospheric pressure. The number of air molecules above a surface decreases as the height of the surface above ground level increases. So atmospheric pressure decreases with an increase in height.
For an object moving at constant speed the distance travelled in a specific time can be calculated using the equation: v = s/t
If an object moves along a straight line, how far it is from a certain point can be represented by a distance–time graph (d-t graph).
The speed of an object can be calculated from the gradient of its d-t graph.
If an object is accelerating, its speed at any particular time can be determined by drawing a tangent and measuring the gradient of the distance–time graph at that time.
The acceleration of an object can be calculated from the gradient of a velocity – time graph.
The distance travelled by an object can be calculated from the area under a velocity – time graph.
Near the Earth’s surface any object falling freely under gravity has an acceleration of about 9.8 m/s2.
An object falling through a fluid initially accelerates due to the force of gravity. Eventually the resultant force will be zero and the object will move at its terminal velocity.
The tendency of objects to continue in their state of rest or of uniform motion is called inertia.
Inertial mass is a measure of how difficult it is to change the velocity of an object.
Inertial mass is defined by the ratio of force over acceleration. m = F/a
Newton’s Third Law:
Whenever two objects interact, the forces they exert on each other are equal and opposite.
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).
Stopping distance = thinking distance + braking distance
Stopping time = thinking time + braking time
Uniform acceleration: v2 - u2 = 2as
When a force acts on an object that is moving, or able to move, a change in momentum occurs.
F = m∆v/t
