Forces (Chapter P8) Flashcards
What is a scalar quantity?
A scalar quantity has magnitude (size) only.
Some examples are: speed, mass, time, energy.
What is a vector quantity?
A vector quantity has magnitude and direction.
Some examples are: displacement, velocity, acceleration, force, momentum.
What is a contact force?
A contact force occurs when two objects touch each other.
Some examples are: Friction, normal contact force, tension, and air resistance.
What is a non-contact force?
A non-contact force does not require two objects to touch each other.
Examples are: Gravity, Electrostatic force, magnetism.
What is Newton’s third law?
“Every action has an equal and opposite reaction” or in other words if object A exerts a force on object B
then object B exerts an equal and opposite force on object A.
What is weight?
The gravitational force of attraction you experience because you are in the Earth’s gravitational field is also known as your weight.
Weight is a force and is measured in Newtons (N).
Weight is measured using a calibrated spring balance (Newton meter)
What is the equation for weight
weight = mass x gravitational field strength
What is the centre of mass of an object?
It is the single point where all the weight of the object can be said to act from
What is a resultant force?
If two or more forces act on an object then these can be replaced by a single force arrow that we call the
“resultant force”.
What is a moment?
A moment of a force is a measure of the turning effect of the force on an object
What is the equation for a moment?
moment = force x perpendicular distance from pivot
What is the principle of moments?
If an object is balanced then the sum of all the clockwise moments acting on it equals the sum of all the anticlockwise moments acting on it.
What is a gear?
Gears are devices that are used to transmit the rotational effects of forces from one place to another.
E.g. a bike gear is used to transmit the rotational effect of the pedal to the wheels.
