P2.3 Flashcards
How do you change the shape of an object?
Compress
Strength
Bend
How many forces are needed to change the shape of an object?
Two or more
Why are certain materials described as plastic?
If they do not return to their original shape when stretched
What does it mean in science if a materials is elastic?
They return to their original shape when the forces are removed
What does a graph of force against extension look like?
Linear until a certain point
What is the point called in a extension against force graph when it is no longer a linear relationship?
The limit of proportionality or the elastic limit
What happens to a spring after the elastic limit?
It doesn’t return to its original shape - permanently deformed
What is Hooke’s 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?
Spring constant (N/m)
———————————
Extension (m)
What are the units for the force exerted by a spring?
Newton (N)
What part of the graph is known as the spring constant?
The gradient of the linear section of the force against extension graph
What does the spring constant determine?
How difficult it is to stretch the spring
What is the formula for energy transferred in stretching?
0.5 x spring constant (N/m) x (extension (m))^2
What is “energy transferred” in a spring equal to?
Work done
What happens when you stretch a material that isn’t a spring?
The relationship between extension and force isn’t linear
What is a gravitational field?
A region where mass experience an attractive force
What is the formula for gravitational force?
Mass (Kg) x gravitational field strength (N/Kg)
What are the units for gravity force?
Newtons (N)
What is gravity field strength or gravity constant?
The measure of the force on 1kg mass when it is in a gravitational field due to another mass
What is the formula for weight?
Mass (Kg) x Gravitational Field Strength (N/Kg) = 10N/Kg
What is weight and what are the units for it?
The force of earth on an object - measured in Newtons (N)
What is the formula for resultant force?
Resultant force (N) = Mass(Kg) x acceleration due to gravity (m/s^2) = (10m/s^2 on earth)
What is acceleration due to gravity on earth?
10m/s^2 (9.81 to be exact)
What is the formula for gravitational potential energy (gpe)?
Mass (Kg) x height (m) x gravitation field strength (N/Kg) =10N/Kg
What is a moment?
The turning effect of a force
What is the formula for moment?
Force (N) x distance (M)
What is the principle of moment?
An object is balanced when the anti-clockwise moment is equal to the clockwise moment
What is the formula for mechanical advantage in levers?
Load - force the lever exerts on the load
———————————————————
Effort - force you exert
What is the rule in pivots?
Distance x effort = distance x load
What is a load?
The force that the lever exerts on the load
What is effort?
The force you exert on the lever
How do cogs transmit forces
If you rotate a small cog, it will make the larger cog rotate
What is the ratio between large and small cogs?
The force x distance is the same for all cogs
What is the formula for pressure?
Force normal to the surface (N)
———————————————
Area of that surface M^2)
What is a hydraulic machine?
A machine made of two pistons connected by a pipe which has the same pressure throughout it
How do you calculate pressure in a hydraulic machine?
Force Force
——— = ————
Area Area
