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P5 - Forces and Motion (L1 to L16 (Excluding L8 - L12) - Coggle Diagram
P5 - Forces and Motion (L1 to L16 (Excluding L8 - L12)
L1 - Scalar and Vector Quantities
A scalar quantity is a quantity with only magnitude, not direction. Examples include speed, mass, distance and energy.
A vector quantity is a quantity with both direction and magnitude. Examples include velocity, displacement, weight, acceleration and force.
Displacement is the distance from one point to another with no change of direction.
Vectors can be added together to get a resultant vector. The length of a vector indicated the magnitude of the vector, the direction of the vector indicates the direction of the quantity.
L2 - Types of Forces
Contact forces are forces that are caused when two objects make contact with eachother. Examples of contact forces include friction, tension, air resistance (drag) and normal contact force.
Non-contact forces occur when two bodies act on eachother without physical contact. Examples include magnetic attraction and repulsion, electrostatic forces and gravitational forces.
Forces are vector quantities.
Newton's third law of motion states that "when body A applies a force on body B, body B applies a force to body A. This force is equal in size, the same type and opposite in direction".
L3 - Resultant Forces
The result of two forces acting on each other is called a resultant force, the larger force - the smaller force will calculate the resultant force. If the forces acting on an object are equal and the resultant force is 0 Newtons, the object will be moving at a constant speed. If there are no forces acting on an object, it is said to be in "equilibrium".
L4 - Gravity and Weight
Mass is a measure of how many atoms there are in an body.
Weight is the effect of mass with respect to gravitational field strength.
Centre of gravity is the point at which an object's weight acts.
Weight = Mass x Gravitational Field Strength
(As long as the gravitational field strength remains the same) Weight and mass are directly proportional to one another (with g as the constant)
L5 - Work Done
Work Done = Force x Displacement
A force does work on an object when it causes a displacement of the object.
1 Joule = 1 Newton-meter
When work is done, not all energy will be converted from potential energy to kinetic, some may be lost as heat energy during friction.
L6 - Elasticity
The extension of a spring is directly proportional to the force applied to the spring (provided the elastic limit has not yet been reached).
Force = Spring Constant x Extension
Required Practical (Hooke's Law)
Method:
Secure a clamp stand to the surface you are working on
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Attach a clamp to the clamp stand
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Attach the spring you will be using to the clamp, it should be vertical
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Secure a ruler to the apparatus so that it is parallel with the spring
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Measure the length of the spring without any force applied
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Hang the first weight increment from the spring, measure the new length of the spring and then calculate the extension
Dependent variable: Extension
Independent variable: Force applied to spring
Graphing the result of the practical will show that force and extension are directly proportional to each other (provided that the limit of proportionality is not reached).
The equation "F = k x e" can be altered if compression is being considered, in which case the equation is "F = k x c", a spring constant can never be negative, nor can force.
The gradient of a force - extension graph is the spring constant.
Control variable(s): Cross-sectional area of spring
L7 - Spring Calculations
Elastic Potential = 0.5(Spring Constant x (Extension^2))
L13 - Speed, Distance, Time
Walking - 1.5 m/s
Running - 3 m/s
Cycling - 6 m/s
Sound - 330 m/s
Distance = Speed x Time
L14 - Distance v Time Graphs
In a distance time graph (distance = y axis, time = x axis), the speed of a body is equal to the gradient of the line representing it.
A straight line indicates a constant speed.
A horizontal line indicates that the body is in equilibrium, it is not moving.
L15 - Velocity v Time Graphs
Acceleration = Change in velocity / Time
Acceleration is measured in m/s^2
Acceleration has the potential to be a negative value, this means that the body is decelerating
A horizontal period in a journey is indicates a constant velocity.
L16 - Continuation of V v T Graphs
To find a journey's displacement, we can calculate the area underneath the line / curve.