Forces Flashcards
What is a vector quantity?
A vector quantity is a quantity that has size and direction
What is a scalar quantity?
A scalar quantity is a quantity that has size
What are the examples of vector quantities?
Examples of vector quantities include force, velocity, displacement, acceleration, momentum
What are the examples of scalar quantities?
Examples of scalar quantities include speed, distance, mass, temperature, time
What are examples of contact forces?
Examples of contact forces include friction, air resistance, tension and normal contact force
What are examples of non-contact forces?
Examples of non-contact forces include gravitational, electrostatic and magnetic
How is a vector quantity represented in a diagram?
In a diagram, vector quantities are represented by an arrow, where the length shows the size and the direction of the arrow shows the direction by which the object is moving`
What is it called when the resultant force is zero?
When the resultant force is zero, that means an object is in equillibrium
How do you work out the resultant force of an object when the arrows are in opposite directions?
When the arrows of an object are in opposite directions, you take the smallest quantity from the biggest quantity
How do you work out the resultant force of an object when the arrows are not facing opposite directions (eg one faces north and the other faces west)
To figure out the resultant force of an object when the arrows are not in opposite directions eg north and west, you draw an arrow from the centre outwards to the point where they meet and measure that arrow with a ruler. The measurement (eg 13cm) is the resultant force (so it would be 13N)
What is Newton’s first law?
Newton’s first law is that if resultant force acting on an object is zero, it will remain stationery.
What does Newton’s first law say about moving objects?
If resultant force acting on a moving object is zero, the object will continue to move in the same direction at the same speed
What is the resultant force?
Resultant force is a force that causes speed and direction of an object to change
What is Newton’s second law?
Newton’s second law states that the acceleration of an object is proportional to the resultant force acting on the object and inversely proportional to the mass of the object
How does mass affect acceleration?
Larger mass = smaller acceleration
Smaller mass = Larger acceleration
How does reultant force affect acceleration?
Greater resultant force = greater acceleration
What is intertia?
Intertia is a resistance to a change in motion
What does inertia depend on?
Inertia depends on it mass
How does mass affect inertia?
Greater mass = more inertia. A greater resultant force is needed
What is inertial mass?
Inertial mass is a measure of how difficult it is to change the velocity of an object
What is Newton’s third law?
Newton’s third law is that whenever two objects interact, the forces they exert on each other are equal and opposite eg equal in magnitude, opposite in direction
Describe the forces that act on a skydiver when they jump out of a plane (5)
1) . Weight acts as the only force when jumping out of the plane due to gravity. This will not change.
2) . Due to weight, the skydiver experiences force acting downwards, meaning they accelerate towards the ground.
3) . Skydiver experiences air resistance which acts upwards.
4) . Their air resistance increases as their velocity increases which eventually balances - no resultant force. The skydiver has reached terminal velocity.
5) . They open their parachute to increase the surface area so air resistance increases meaning resultant force then acts upwards. Velocity decreases meaning there is no resultant force and they land safely.
What is the momentum of an object that is not moving?
An object that isn’t moving has no momentum
What is conservation of momentum?
Conservation of momentum = in a closed system, the total momentum before an event is equal to the total momentum after an event
How do you calculate momentum?
Momentum = mass x velocity
How can we reduce the danger from a rapid change in momentum?
We can reduce the danger from a rapid change in momentum by making the change in momentum happen over a longer time
What are the safety devices that slow momentum change?
Safety devices that slow momentum change include airbags, seatbelts, bike helmets, cushioned surfaces and crash mats
