P8 Forces in balance Flashcards
What is displacement?
Distance in a given direction
what is a vector quantity?
A vector quantity has magnitude and direction
What is a scalar quantity?
A scalar quantity has only magnitude
what are five examples of vector quantities?
- Acceleration
- Force
- Momentum
- Weight
- Velocity
what are six examples of scalar quantities?
- Speed
- Distance
- Time
- Mass
- Energy
- Power
How to represent a vector quantity
A vector quantity can 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 third law?
States that when two objects interact with each other, they exert equal and opposite forces on each other
What is a contact force?
A force that acts on objects only when the objects touch each other
what is Newton’s first law?
States that if the forces acting on object are balanced, the resultant force on the object is zero, and:
- if the object is at rest, it stays stationary
- if the object is moving, it keeps moving with the same speed and in the same direction
What does it mean if the resultant force on an object is zero?
If only two forces act on an object with zero resultant force, the forces must be equal to each other and act in opposite directions
What is the resultant force?
A single force that has the same effect as all the forces acting on an object
How to calculate the resultant force when an object is acted on by two unequal forces in opposite directions?
The resultant force is equal to the difference between the two forces, in the direction of the larger force
How to calculate the resultant force when an object is acted on by two forces acting along the same line?
The resultant force is equal to the sum of the two forces, in the same direction as the two forces
A free-body diagram
Shows the forces acting on an object without any other objects or other forces shown
How to calculate the moment of a force
moment = force x perpendicular distance
M = F x d
How to increase the moment of a force in general
- Increase the magnitude of the force
- Increase the distance
How the moment of a force can be increased - spanner
The turning effect of a force, called the moment of the force, can be increased by:
- increasing the size of the force
- using a spanner with a long handle
What is the moment of a force?
A measure of the turning effect of the force on an object
what are levers?
Can be used to exert a force that is greater than the effort
Load
The weight of the object
What three parts make up a lever system?
- Load
- Effort
- Pivot
How can a lever be used as a force multiplier?
- If the distance between the effort and pivot is greater than the distance between the pivot and load, the force applied on the load is greater than the effort force
- This is because the moment on both the effort and load must be the same
Examples of contact forces
- Friction
- Air resistance
- Tension
- Normal contact force
Examples of non-contact forces
- Gravitational force
- Electrostatic force
- Magnetic force
What is a force?
A push or pull that acts on an object due to the interaction with another object
What is a contact force?
A force that acts on objects only when the objects touch each other
What is a non-contact force?
A force that acts on objects at a distance, the objects are separated
Why is a door handle placed on the opposite side of the hinge?
- For a given force, the perpendicular distance from the pivot is larger
- This creates a larger moment to make it easier to open the door
- Opening a door with a handle close to the pivot would be much harder, and require a lot more force
What is the principle of moments?
States that if an object is unbalanced, the total clockwise moment about a pivot equals the total anticlockwise moment about the pivot
what are the two categories that all forces can be split into?
contact and non-contact forces
give three examples of contract forces
- friction
- tension
- air resistance
give three examples of non-contact forces
- magnetic
- gravitational
- electrostatic
