Chapter 8 - Forces in balance Flashcards
Displacement
Distance travelled in a certain distance
Distance
How far an object moves
Vectors
Quantities that have both magnitude and a direction
Scalers
Quantities that have magnitude, no direction.
Examples of vectors (6)
Displacement, velocity, acceleration, force, weight, momentum
Examples of scalers (4)
Mass, speed, time, distance
Vectors shown through arrows
The direction of the arrow shows the direction of the vector, and the length of the arrow shows the magnitude of the vector
Scale diagrams
A diagram is used to show when more than one force is acting upon an object.
Force
A push or pull acting on an object because of an interaction with another object.
Contact force
A force that is exerted only when 2 objects touch
Non-contact force
A force that one object can apply to another object without touching it.
Examples of contact forces (4)
Friction, air resistance, tension, normal contact force.
Examples of non-contact force (3)
Gravitational forces, electrostatic forces, and magnetic forces.
Newton’s third law of motion
When 2 objects interact with each other, they exert an equal and opposite force on each other.
Driving force
The force of a vehicle that makes it move.
Friction in cars
A car can only move forward due to the friction between the car and the ground. Friction only acts where the tyre is in contact with the ground
Resultant force
A single force that has the same effect as all the forces acting on the object.
Zeron resultant force
When all forces are balanced the object is stationary or travelling at a continuos speed.
Newton’s first law of motion
An object at rest stays at rest and an object in motion stays in motion with the same speed and same direction unless acted upon by an unbalanced force.
Unbalanced forces
Forces that cause a change in the motion of an object. The object’s movement depends on the size and direction of the resultant force.
Free body diagram
A diagram that shows all the forces acting on an object.
Calculating the resultant force.
The resultant force is equal to the difference between the forces and in the direction of the largest force.
How to increase momentum
Increase the size of the force or increase the distance from pivot.
The weight of an object is called?
A load
The force applied to the lever is called?
Effort.
Pivot
The point at which the lever turns.
Examples of force multipliers.
Bottle openers and a pair of scissors.
The line that a force acts along is called>
Line of action
Force multiplier
A lever where the load is bigger than the effort.
Gears
They act like levers as they multiply the effect of a turning force.
How gears work.
Gear wheels exert an equal and opposite force on each other when their edges are in contact. The force of each gear acts perpendicular to the centre of the wheel
Effects of sizes of gears
The turning force of a larger wheel acts further from the shaft than the turning force for a smaller gear. It means that the turning effect of the wheel shaft is bigger than the turning effect on the engine shaft
Low gear
Low speed and high turning effect
High gear
High speed and low turning effect
Centre of mass
The point at which the mass of an object comes to rest and has no rotational forces when hanging. This is because the centre of mass is directly below then point of suspension.
Identifying the centre of mass
If an object has more than one line of symmetry, the centre of mass is the pint at which the lines meet.
Suspended equilibrium
The point at which an object comes to rest and has no rotational forces when hanging. This is because the centre of mass is directly below the point of suspension
Principle of moments
The sum of all the clockwise moments about any point = the sum of all anticlockwise moments about the same point.
A balanced seesaw
The monet of the left hand side must equal the moment of the right hand side for the seesaw to be balanced.
Parallelogram of forces
A geometrical method is used to find the resultant force of two forces that don’t act on the same line.
How to create a parallelogram of forces.
Draw the vectors of the forces at the correct angles to each other. Using a compass, complete the parallelogram. Measure the distance from the starting point to the opposite point of the parallelogram and that is the resultant force
Resolution of forces
The process of considering a force in terms of two perpendicular components, which together have the same effect on an object as the force
Conditions for an object to be in equilibrium
There are zero resultant forces on the object and the forces acting on the object have no overall turning effect.
Identifying an object in equilibrium when the lines of action of the forces are parallel
The sum of the forces in one direction must be equal to the sum of the forces in the other direction.
Identifying an object in equilibrium when the lines of action of the forces are not parallel.
The forces can be resolved into 2 components along the same perpendicular line. These components must then balance out if the object is in equilibrium.
