Forces - paper 2 Flashcards
To revise forces (Paper 2)
Define a scalar
A quantity that only has magnitude.
Give some examples of scalar quantities
Speed, distance, time, mass, volume
Define a vector quantity
A quantity that has magnitude and direction.
Give some examples of vector quantities
Velocity, displacement, acceleration, momentum, any force
State the difference between distance and displacement
Distance is a scalar - doesn’t involve direction
Displacement is a vector and is measured in a straight line from the start point to the finish point and the direction of that straight line.
State the difference between speed and velocity
Speed is a scalar - only has magniture
Velocity is a vector - has magniture and direction
State some examples of non contact forces
Friction, air resistance, drag, upthrust, tension, normal contact force
State some examples of contact forces
Gravity, magnetism, electrostatic attraction or repulsion
State the equation with all units for Weight
weight (N) = mass (kg) × gravitational field strength(N/kg)
What is the mathematical relationship between weight and mass.
They are directly proportional, if mass doubles then does weight
What equipment can be used to measure weight?
Weight is measured using a calibrated spring-balance called a newtonmeter
Define a resultant force
When a number of forces acting on an object may be replaced by a single force that has the same effect as all the original forces acting together.
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Units of force
Newtons (N)
When is work done?
When a force causes an object to move through a distance
What is the relationship between work done and energy transferred
Work done = energy transferred
State the equation and all units for work done
work done (J) = force (N) × distance moved along the line of action of the force (m)
Define 1 joule of work
One joule of work is done when a force of one newton causes a displacement of one metre.
1 joule = 1 newton-metre
State 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.
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State Hookes law equation with all units
force (N) = spring constant (N/m) × extension (m)
When an object is stretched or squared what form of energy does it store?
Elastic potential energy.
Define elastic deformation
When the forces are removed the object returns to its original length
Define inelastic deformation
When the forces are removed the object doesn’t returns to its original length, it stays permanently stretched.
Define a moment
The turning effect of a force
State the equation for a moment, with all units
moment of a force (Nm) = force (N) × perpendicular distance (m)
If an object is balanced what can you say about the clockwise and anticlockwise moments
They must be equal
Define a fluid
Either a liquid or gas, particles must be able to move past each other
State the equation for pressure with all units
pressure = force / area
Pressure - Pa
Force - N
Area - m2
What is the relationship between pressure from a liquid and depth
As depth increases pressure increase due to a greater number of particles and force pushing on the object.