Physics Revision - Science Flashcards
What is displacement?
How far you are from the starting point - including direction.
What is distance?
How far you have travelled.
A person walks 4km from their home, then 4km back and then 2 km south.
What is the displacement and distance?
The displacement is 2 km south from their home.
The distance is 4 + 4 + 2 = 10 km
What is the equation for average speed?
And how do you find the other variables?
(Hint - average speed triangle)
Average speed (Sav) = distance (d) / time (t)
Time (t) = distance (d) / average speed (Sav)
Distance (d) = average speed (Sav) x time (t)
What is a vector quantity?
A thing that measures both magnitude and direction.
What is a scalar quantity?
A thing that measures only magnitude.
Is speed a scalar or vector quantity?
Scalar
What is velocity?
A vector quantity that measures the speed in a particular direction.
What is the average velocity equation?
And how do you find the other variables?
(Hint - average velocity triangle)
Average velocity (Vav) = displacement (d) / time (t)
Time (t) = displacement (d) / average velocity (Vav)
Displacement (d) = average velocity (Vav) x time (t)
How do you find the displacement in a velocity time graph?
Calculate the area under the graph and calculate the total area of all the shapes under the graph.
(Distance is all added together even if there are negative numbers)
What is acceleration?
The rate at which the velocity or speed of an object changes.
What is the acceleration value of 10 m/s2 or 9.8 m/s2 called?
Acceleration due to gravity.
How do you calculate acceleration?
And how do you calculate other variables?
(Hint - acceleration triangle)
Acceleration (Aav) = change in velocity / change in time or final velocity - starting velocity / final time - starting time.
Change is velocity = acceleration x change is time
Change in time = change in velocity / acceleration
What is Newton’s first law called?
The law of Inertia
What does Newton’s first law state and mean?
States that ‘An object remains at rest or in a constant motion in a straight line unless acted on by a net unbalanced force.’
This means that an object with two forces equal in magnitude and opposite in direction (push and pull) has balanced forces and the motion remains the same. To cause movement or motion another force must be added to cause the forces to become unbalanced.
What is Inertia?
Inertia is the tendency of an object to resist change in motion and keep in the existing state of motion.
What is an example of Newton’s First Law?
When someone is sitting on a chair, the chair is being pulled down due to gravity (its weight force). It doesn’t move because there is another force, equal in magnitude to the weight force but acting in the opposite direction, pushing the chair up from the surface.
An example of Inertia is when a passenger of a vehicle is not wearing their seatbelt and the car comes to a stop, the passenger will continue to move forward due to inertia.
What does Newton’s second law state and mean?
States that ‘The acceleration of an object is directly related to the magnitude and direction of the net force acting on the object and inversely related to the mass of an object.’
Net force (Fnet) = mass (m) x acceleration (a)
Mass (m) = Net force (Fnet) / acceleration (a)
Acceleration (a) = Net force (Fnet) / mass (m)
What is net force?
The vector sum of all the forces acting on an object.
If the forces are acting in opposite directions, it is force 1 - force 2.
If the forces are acting in the same direction it is force 1 + force 2.
What is weight?
Weight is the force from gratify acting on an object and is measured in Newtons (N).
Weight (w) = mass (m) x gravitational acceleration (g)
Mass = weight (w) / gravitational acceleration (g)
Gravitational acceleration (g) = weight (w) / mass (m)
What does Newton’s third law state and mean?
States that ‘For every action, there is an equal and opposite reaction.’
The action force is the initial force of an object while the reaction force is the force acting in the opposite direction to the initial force. Action-reaction pairs always act on different objects and can not cancel each other out.
What is an example of Newton’s Third law?
When you lean against a wall you exert force onto the wall (the action force) so the wall exerts a force onto you (the reaction force).
What is momentum?
It is mass in motion and is the product of the mass and velocity of an object.
What is the law of conservation of momentum?
The law of conservation of momentum states that in an isolated system (the set of objects that interact in a collision), the total momentum does not change during a collision, however momentum is passed along from one object to another.
This means the initial momentum and final momentum are equal.
