P9 Forces Flashcards
What’s the definition of scalar?
Quantities that only have a magnitude (e.g., distance and speed
What does Vector mean?
Quantities that have magnitude and a direction (e.g., velocity and force)
What can a force be?
It can be a push or pull on an object caused by an interaction with another object. Forces are vector quantities.
Are forces scalar or vector?
Vector quantities
When do contact forces occur?
When two objects are touching each other. Like friction or air-resistance.
When do non-contact forces act?
At a distance (without two objects touching), like gravitational force or magnetic force.
when do opposite and equal force occur?
When an object exerts a force on another object.
What causes gravity close to the earth?
The planet’s gravitational field strength.
Weight is the force acting on an object due to…
Gravity.
The weight of an object can be considered to act at the object’s…
Center of mass.
The weight of an object can be measured using…
A calibrated spring balance (newtonmeter).
What is the equation for weight?
Weight= mass (kg) X gravitational field strength (N/kg)
W= m g
Weight and mass are … proportional to each other
Directly
What can weight and mass be written as when together?
W = m
True or false?
If two or more objects act on an object along the same line , their effect is the same as if they were replaced with a single resultant force.
True!
The resultant force is the sum of … if they act in the same direction
The magnitudes of the forces
The resultant force is the … between the magnitudes of the forces if they act in opposite directions.
Difference
When are the forces said to be balanced?
When the resultant force on an object is zero
Free body diagrams are used for what?
they use arrows to show all the forces acting on a single object.
On a free body diagram, what does the arrow length represent?
The magnitudes of the force.
On a free body diagram what does the direction of the arrow show?
The direction of the force.
What can you use scale forces for?
They can be used to find the resultant of two forces which are not acting along the same line
How do you use a scale drawing?
The forces are drawn end to end. The resultant can then be drawn between the two ends, forming a triangle.
What is deformation?
A change in the shape of an object caused by stretching, squashing (compressing), bending, or twisting .
How many forces have to act on a stationary object to deform it rather than make it move?
More than one.
What is elastic deformation?
When the object can go back to it’s original shape and size when the forces are removed.
What’s inelastic deformation?
When the object does not go back it’s original shape or size when forces are removed.
What calculation is used to calculate spring constant?
Force applied (N) = spring constant (N/m) X extension
F = k e
if a force that stretches or compresses an object does work on it, where will the energy be transferred to?
The object’s elastic potential store.
What is the equation for elastic potential energy?
Elastic potential energy (J) = 1/2 X spring constant X (extension)^2 (m^2)
Ee = 1/2 k e^2
A force or system of forces can cause an object to…
Rotate
What is the turning effect of the force called?
The moment
What’s the equation for a moment of a force?
Moment of a force (Nm) = force (N) X distance (m)
M = F d
If an object is balanced, the sum of the clockwise moment equals…
The sum of the anticlockwise moments.
What can lever and gears be used for?
To increase the moment of a force, making it easier to lift or rotate an object
A lever allows a large moment of force to be produced by…
Allowing force to be applied further from the pivot.
