SP15 Flashcards
(21 cards)
What are elastic objects?
Objects that can return to their original shape when the forces that deform them are removed.
What are inelastic objects?
Objects that will keep their new shape after the forces are removed.
How do springs react to forces?
Springs are the most common examples of objects that are elastic when the forces acting on them are small and start to behave inelastically if the forces become too big.
What are springs usually made out of and how do they behave?
Metals that behave elastically up to a certain point and become permanently deformed if the forces used to stretch them are too big.
How do we calculate the extension of a spring?
Extension of spring = stretched length - original length
Describe the graph for a metal spring of force against length.
Usually has a linear relationship which becomes non-linear if the spring is stretched too far/reaches limit of proportionality. It is also not directly proportional since the line doesn’t pass through the origin.
Describe the graph for a metal spring of force against extension.
Linear relationship until the limit of proportionality where it becomes non-linear. They are directly proportional since the line passes through the origin.
What is Hooke’s Law?
Extension is directly proportional to the force.
Force = spring constant x extension | F = k . x
Describe the graph for a rubber band of force against extension.
Non-linear relationship, thus not as easy to make predictions about extension of a rubber band for a certain force.
What is the limit of proportionality?
The point which if exceeded, the spring extension will no longer be proportional to the force.
What is the spring constant?
The amount of force needed to produce an extension of 1m (N/m).
How do we calculate the energy transferred in stretching?
E = 1/2 . k . x² OR E = 1/2 . F . x
How do we carry out the springs investigation?
Check teacher notes slide 23.
What is pressure?
A measure of the force on a unit of surface area, where the force is normal (at right angles) to the surface.
How do we calculate pressure?
Pressure (Pa) = force normal to the surface (N) / area of surface (m²)
What is the total pressure on a diver?
The pressure due to both the water and the air above.
How do we calculate the pressure due to a column of fluid?
Pressure (Pa) = height of column (m) x density of liquid (kg/m³) x gravitational field strength (N/kg) | P = h x ρ x g
How do we calculate pressure difference?
Pressure difference = depth difference x ρ x g | Δρ = Δh x ρ x g
How do we calculate upthrust?
Upthrust = pressure difference x area | U = Δρ x a
How can we also calculate upthrust?
The weight of fluid displaced by the object.
