P2.3 Forces In Action Flashcards
Momentum equations
Momentum(p) = mass(m) x velocity(v)
Equation for final velocity after a collision:
m1v1 + m2v2 = (m1 + m2) * vfinal
m = mass
v = velocity
vfinal = final combined velocity of both objects after the collision
Kg into Newtons
1kg = 10N
10N is earth gravitational field strength (N/kg) represented by g
Explain relationship between force applied and extension of an elastic object.
Extension is directly proportional to the force applied, provided that the limit of proportionality is not exceeded
Inelastic deformation
Deformation which results in the object being permanently stretched
Object doesn’t return to its original shape when the force is removed
Equation relating force, spring constant and extension
Force = Spring Constant x Extension
F = kx
Force (N), Spring Constant (N/m), Extension (m)
NB: spring constant is how STIFF a spring is - large value = more stiff
Hooke’s law
Force applied is DIRECTLY PROPORTIONAL to 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
| _—————
| /‾ <—— The graph stops being linear here
| /
|/_______________
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
Equation for elastic potential energy
Energy (J) = ½ × Spring Constant (N/m) × (Extension (m))²
Weight
Force that acts on an object due to gravity and the object’s mass
Weight (N) = mass (kg) x gravitational field strength (N/kg) (10N/kg on earth)
What quantities does weight depend on
Object’s mass
Gravitational field strength at the given position in the field
What is meant by an object’s centre of mass
Single point through which an object’s weight can be considered to act through
What type of field does all matter have
Gravitational field
How does the gravitational field of an object change as the object becomes more massive
Field strength increases
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
Gravitational field strength varies for each planet
Weight is the product of mass and gravitational field strength
What piece of equipment can be used to measure an object’s weight
Calibrated spring-balance or newton-meter
Alternative name for the turning effect of a force
Moment
Equation used to calculate the moment of a force
Moment of force (Nm) = Force (N) × Distance (m)
What distance measurement is used when calculating a moment
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 moments are equal to the anticlockwise moments
What does the direction of a resultant moment acting on an object tell you
Direction that object will rotate around pivot point
In any fluid, at what angle do the forces due to pressure act on a given surface
Right angles (normal to) the surface
What can be said about the pressure in a simple hydraulic system
Pressure in the fluid is constant through the fluid (it cannot be compressed or expand)
How a simple hydraulic lift works
Pressure is constant in fluids
Force applied on each platform is equal to the product of pressure and area (F = p x A).
One platform has a larger area than the other, meaning the force produced is greater than the force applied to the smaller platform
Equation for gravitational potential energy
GPE = mass x gravitational field strength x height
