P8(Forces In Balance) Flashcards
What is displacement
a measure of how far something is from its starting position, along with its direction
What is a vector
A physical quantity which has magnitude and direction
What is a scalar
A quantity that has magnitude but no direction
How can a vector quantity be represented
By an arrow in the direction of the vector and of length in proportion to the magnitude of the vector
What is newton’s 3rd law
When 2 objects interact they always exert equal and opposite forces on each other
Forces can …
-Change the shape of an object
-Change an objects motion
-Change the objects state of rest
What is a contact force
A force that acts on objects only when the objects touch each other
What is newtons 1st law of motion
If the forces acting on an object are balanced, the resultant force on the object is zero
What is the resultant force
A single force that has the same effect as all the forces acting on an object
If the resultant force on an object is:
-Zero, the object stays at rest or at the same speed and direction
-greater than zero, the speed or direction of the object will change
If an object is acted on by 2 unequal forces acting in opposite directions the resultant force is:
-equal to the difference between the 2 forces
-in the direction of the larger force
If 2 forces act on an object along the same line the resultant force is:
-their sum, if the forces act in the same direction
-their difference, if the forces act in opposite directions
What is a moment
A measure of the turning effect of the force on an object
The moment(turning effect of the force) can be increased by:
-increasing the size of the force
-using a spanner with a longer handle
Levers can be used to …
Exert a force that is greater than the effort
What is the formula for moments
Low gears gives …
Low speed and a high turning effect
High gear gives …
High speed and a low turning effect
Gears are used to …
Change the moment of a turning effect
What is centre of mass
The centre of mass of an object is the point at which its mass can be thought of as being concentrated
When an object is freely suspended…
It comes to rest with its centre of mass directly underneath the point of suspension
What is the principal of moments
the sum of all the clockwise moments about any point = the sum of all the anticlockwise moments about that point
All the forces acting on an object that don’t pas through a fixed point…
Can turn an object about that point
The direction of the force and position of the fixed point …
Determines whether the moment acts clockwise or anticlockwise
What’s the formula to calculate the force needed to stop an object turning
The parallelogram of forces is used …
-to find the resultant of two forces that do act along the same line
-the resultant is the diagonal of the parallelogram that starts at the origin of two forces
Resolving a force means
Finding perpendicular components that have a resultant force that is equal to the force
For an object in equilibrium …
The resultant force is zero
An object at rest is in equilibrium because…
The resultant force on it is zero
