P2.3 Forces In Action Flashcards
How do you change the shape of an object
Compression
Tension/stretching
Bending
What is a plastic material
A material that becomes deformed when you apply a force and does not return to its original shape when you remove the force
What is an elastic material
An object that returns to its original shape when you remove a force
What type of relationship does force and extension have
A linear relationship
They are directly proportional
What is a linear relationship
One where a straight line passes through (0,0)
What is the Limit of proportionality
The point where extension is no longer proportional to force
What is the elastic limits
The point beyond which an object does not return to its original shape when the force is removed
What is Hookes Law
The extension of a spring is proportional to the force until you reach the limit of proportionality
What is the equation for the force exerted by a spring
Force exerted by a spring (N) = spring constant (N/m) ✖️ extension (m)
What is the spring constant
It tells you how stiff an object is
How do you calculate the energy transferred in stretching a spring
Energy transferred (J) = 0.5 ✖️spring constant (N/m) ✖️ (extension)2
What type of relationship exists between force and extension when you stretch an elastic band?
Non linear
What happens to the stiffness when you blow a balloon
First the rubber is stiff
Once you start blowing it up it requires less force to produce extension
It then becomes stiffer again
What is a gravitational field?
A region where a mass experiences an attractive force
What is the equation for gravity force
Gravity force (N) =. Mass (kg) ✖️gravitational field strength (N/kg)
What is gravitational field strength
The measure of the force on a 1Kg mass when it is in a gravitational field
Does mass change
No
What is weight
The force of the earth on an object
How do you calculate weight
Weight (N) = mass (kg) ✖️gravitational field strength
What is gravitational potential energy
The energy transferred to a gravity store when you lift an object in a gravitational field
How do you calculate gravitational potential energy
Gpe (J) = mass x gravity x height
What is a pivot?
The point about which forces act to produce turning effects
What is a moment
The turning effect of a force
How do you calculate the moment of a force
Moment of a force (Nm) = force x distance
What is the principle of moments?
An object is balanced if the anti-clockwise moments are equal to the clockwise moments about the pivot
F1D1 = F2D2
What is a force multiplier
A factor that greatly increases the effectiveness of a force
What is a lever and what does it do?
An object that won’t bend with a pivot
A force applied at one end produces a force in the opposite direction at the other end
It transmits forces by rotating about a pivot
What is the effort
The force you apply (to the lever )
What is the load?
The force that you are trying to move
The force that the lever exerts of the load
How do you calculate the mechanical advantage?
Load ➗ effort
How do gears transmit forces?
If you make a small cog rotate with a large force it will make a larger cog rotate.
The bigger cog will exert a bigger force, but will not move as far
You can use gears to change the direction in which the rotating force acts or the speed at which it rotates.
How does pressure in a fluid cause a force
The pressure in a fluid produces a force at right angles to any surface
How do you calculate pressure
Force (N) ➗ area (m2)
What is a hydraulic machine
A machine that uses a liquid to transmit a force
Made of two pistons connected by a pipe. When you push on one piston the pressure is transmitted through the liquid and the other piston moves
