Work Done, Energy, Power + Materials Flashcards
How is work done calculated?
Work done (W) = Force × Distance × cos(θ), where θ is the angle between force and motion.
What is power in terms of energy transfer?
Power is the rate of energy transfer, given by Power = Work Done / Time or Power = Force × Velocity.
How can work done be found when force is variable?
By calculating the area under a force-displacement graph.
How is efficiency calculated?
Efficiency = (Useful Power Output / Total Power Input) × 100%.
What does the principle of conservation of energy state?
Energy cannot be created or destroyed, only transferred from one form to another.
How is gravitational potential energy calculated?
GPE = Mass × Gravitational Field Strength × Height (E_p = mgh).
How is kinetic energy calculated?
Kinetic Energy = 1/2 × Mass × Velocity² (E_k = 1/2 mv²).
What is the equation for Hooke’s Law?
F = kΔL, where k is the spring constant and ΔL is the extension.
What is the limit of proportionality?
The point beyond which Hooke’s Law is no longer obeyed.
What is the difference between tensile stress and tensile strain?
Tensile stress = Force / Cross-sectional area, Tensile strain = Extension / Original length.
What is elastic strain energy and how is it calculated?
It is the energy stored when stretching a material, calculated as Elastic Strain Energy = 1/2 × Force × Extension.
What happens when a material reaches its breaking stress?
The material will fracture or break apart.
How do plastic and brittle materials behave differently under stress?
Plastic materials extend significantly before breaking, while brittle materials fracture at low extensions.
What does a stress-strain graph show?
It represents the behavior of a material under stress and indicates properties like the ultimate tensile stress (UTS).
What is Young’s modulus and how is it calculated?
Young’s modulus measures stiffness, given by E = Tensile Stress / Tensile Strain.
How can Young’s modulus be determined from a graph?
By calculating the gradient of the linear portion of a stress-strain graph.
What happens to the energy in an elastic stretch?
It is stored as elastic strain energy and fully recovered when the force is removed.
What happens to energy in a plastic deformation?
Work is done to move atoms apart, and energy is dissipated as heat rather than stored.
How do crumple zones in cars help in a crash?
They plastically deform to absorb kinetic energy, reducing the impact on passengers.
What is ultimate tensile stress (UTS)?
The maximum stress a material can withstand before breaking.
What happens to a spring’s energy when it is stretched and released?
It alternates between elastic strain energy and kinetic energy, similar to a bouncing ball.
