P8 Forces In Balance Flashcards
Displacement
Distance in a given direction
Vector quantity
A physical quantity which has magnitude and direction
Scalar quantity
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
Newton’s third law of motion
When two objects interact, they exert equal and opposite forces on each other.
Contact force
A force that acts on objects only when the objects touch each other
Newton’s first law
an object remains in the same state of motion unless a resultant force acts on it. If the resultant force on an object is zero, this means:
- A stationary object stays stationary
- A moving object continues to move at the same velocity (at the same speed and in the same direction)
Resultant force
A force that has the same effect as all the forces acting on an object
What do you call a diagram that shows the forces acting on an object?
Free-body diagram
If two 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
Load
The weight of the object
Effort
The force the person applies
Moment =
Force x distance
Moment
A measure of the turning effect of the force on an object
Low gear gives
Low speed and a high turning effect
High gear gives
High speed and a low turning effect
How do you increase the moment of a turning effect?
A small gear wheel needs to drive a large gear wheel
Centre of mass of an object
The point at which its mass can be thought of as being concentrated
An object is freely suspended if
It returns to its equilibrium position after the turning force is taken away
When an object is freely suspended, it comes to rest with…
Its centre of mass directly underneath the point of suspension
An object is in equilibrium if
The clockwise moment = the anticlockwise moment
The parallelogram of forces is used to
Find the resultant force of two forces that do not act along the same line
How to calculate the resultant force of two forces which don’t act along the same line
The resultant is the diagonal of the parallelogram that starts at the origin of the two forces
