P2.3 - Forces in action Flashcards
Explain the relationship between the force applied and the extension of an elastic object.
extension is directly proportional to the force applied
provided that the limit of proportionality is not exceeded
What is meant by an inelastic (plastic) deformation?
A deformation which results in the object being permanently stretched.
State the equation relating force, spring constant and extension. Give appropriate units
Force = Spring Constant x Extension
F = kx
Force (N), Spring Constant (N/m) Extension (m)
What is Hooke’s law?
force applied is directly proportional to the extension of an elastic object.
At what point does Hooke’s law no longer apply?
The limit of proportionality.
What does the limit of proportionality look like on an
extension-load graph?
Where the graph stops being linear.
What type of energy is stored in a spring when it is stretched?
Elastic potential energy.
What can extension be replaced with in
the equation for spring force?
Compression
What is the equation for elastic potential energy? Give SI units for all quantities involved
E = ½ k x2
Energy = ½ x Spring Constant x (Extension)²
Energy (J), Spring Constant (N/m), Extension(m)
What is weight?
The force that acts on an object due to gravity and the object’s mass.
What quantities does weight depend on?
● The object’s mass.
● The gravitational field strength at the given position in the field.
What is the unit used for weight?
Newton
What is the equation used to calculate weight?
Weight (N) = mass (kg) x gravitational field strength (N/kg)
What type of field does all matter have?
A gravitational field.
What is the acceleration of an object falling in free
fall with no resistive forces acting?
10 m/s²
Why would your weight be different if you were on a
different planet?
The gravitational field strength varies
for each planet.
What piece of equipment can be used to measure an
object’s weight?
A calibrated spring-balance or newton-meter.
What is an alternative name for the turning effect of
a force?
A moment.
State the equation used to calculate the moment of a force. Give appropriate units
Moment of force = Force x Distance
Moment (Nm), Force (N), Distance (m)
What distance measurement is used when calculating a moment?
The perpendicular distance from the pivot to the line of action of the force.
If an object is in equilibrium, what can be said about
the moments acting on the object?
Clockwise = anticlockwise
What can be said about the pressure in a simple
hydraulic system?
The pressure in the fluid is constant through the fluid (it cannot be compressed or expand).
Explain how a simple hydraulic lift works.
● The pressure is constant in the fluid.
● Force applied on each platform is equal to the product of pressure and area (F = pA).
● One platform has a larger area than the other, meaning the force produced is greater than the force applied to the smaller platform.
