A-Level Physics: Mechanics: Overview

when can the SUVAT equations be used?

when an object is moving at uniform acceleration

what is the acceleration due to gravity?

9.81ms^-1

what is distance?

scalar quantity which describes the amount of ground an object has covered

what is displacement?

overall distance travelled from starting position

what is speed?

scalar quantity describing distance travelled per unit time

what is velocity?

rate of change of displacement

what is acceleration?

rate of change of velocity

what is uniform acceleration?

where the acceleration of an object is constant

what do acceleration-time graphs represent?

change in velocity over time

what does the area under an acceleration-time graph represent?

change in velocity

what does a velocity-time graph represent?

change in velocity over time

what does the gradient of a velocity-time graph represent?

acceleration

what does the area under a velocity-time graph represent?

displacement

what do displacement-time graphs show?

change in displacement over time

what does the gradient of a displacement-time graph represent?

velocity

what is instantaneous velocity?

velocity of an object at a specific point in time

how can instantaneous velocity be found?

by drawing a tangent to the graph at a specific point in time and calculating the gradient

from what graph can instantaneous velocity be found?

displacement-time graph

what is average velocity?

velocity of an object over a specified time frame

how can average velocity be found?

by dividing final displacement by time taken

what are scalar quantities?

quantities describing only the magnitude, and not direction

what are vector quantities?

quantities describing both magnitude and direction

what are examples of scalar quantities?

distance, speed, mass, temperature

what are examples of vector quantities?

displacement, velocity, force, weight, acceleration

how can direction be labeled on a vector quantity?

through absolute direction (north, east), a relative direction (left, right) or by the angle made with the horizontal

what is meant by resolving a vector?

where a vector is split into two parts which are perpendicular to each other

in what ways can vectors be resolved?

calculation and scale diagram

how can vectors be resolved by calculation?

by the formulas x = V cos theta, y = V sin theta

what is the method for resolving a vector by scale drawing?

choose an appropriate scale and make note of it by the diagram, use a ruler and protractor to draw the vector as described in the question. draw the vector’s horizontal ad vertical components, making sure they meet in a right angled triangle, then measure the value of the vectors using initial scale

what are two methods of adding vectors?

calculation and scale drawing

when should vectors be added by calculation?

when the two vectors are perpendicular to each other

when should scale drawings be used to add vectors?

when the angle is something other than 90

what is the relationship between vertical and horizontal components of projectile motion?

the components are independent of each other, so they are evaluated sepetarely

when can the uniform acceleration formula be used to evaluate vertical and horizontal motion?

when the acceleration is constant

what is a free-body diagram?

a diagram which shows all the forces that act on an object

what does a free-body diagram show?

each of the forces acting on the object and how they compare with each other depending on magnitude

what does newton’s first law state?

when object at rest will remain at rest, an object traveling at a constant velocity will remain at a constant velocity

what does newton’s second law state?

the acceleration of an object is proportional to the resultant force experienced by an object (F=ma)

what can newton’s second law be used to find?

resultant force, mass or acceleration (if two of the others are known)

what is the condition for newton’s second law being used to find components?

the mass of the object must be constant

how can newton’s first law be derived from newton’s second law?

by substituting a resultant force of 0N, which gives an acceleration of 0ms^-2

when does terminal velocity occur?

where frictional forces acting on an object and driving forces are equal

what can be said about the effects of terminal velocity?

there is no resultant force and so no acceleration so the object moves at a constant velocity

explain the skydiving terminal velocity example.

as a skydiver leaves the plane they accelerate because their weight is greater than the air resistance acting on them. as their speed increases the magnitude of air resistance also increases, until the weight and air resistance become equal

what is gravitational field strength?

force per unit mass exerted by a gravitational field on an object

how can gravitational field strength be calculated?

g=F/m

what is weight?

gravitational force that acts on an object due to its mass

how is weight calculated?

by multiplying the object’s mass by the gravitational field strength

what is the formula for weight?

mass x gravity

what does newton’s third law state?

for each force experienced by an object, the object exerts an equal and opposite force

what is momentum?

product of mass and velocity of an object

what is the formula for momentum?

mass x velocity

what does the principle of conservation of linear momentum state?

momentum is always conserved in an interaction where no external forces act

what is the condition for principle of conservation of linear momentum?

no external forces act

what is the moment of a force?

force multiplied by the perpendicular distance from the line of action to the force to the point

what is the formula for moment of a force?

force x perpendicular distance

what does the principle of moments state?

for an object in equilibrium, the sum of anticlockwise moments about a pivot is equal to the sum of clockwise moments

what is the centre of gravity of an object?

the point at which gravity appears to act

where will the centre of gravity be if the object is described as uniform?

exactly at the object’s centre

what is work done defined as?

force causing a motion multiplied by the distance travelled in the direction of the motion

what is the formula for work done?

force x distance in direction of motion

what is kinetic energy?

energy an object has due to its motion

what is the formula for kinetic energy?

what is gravitational potential energy?

what is the formula for the change in gravitational potential energy near the earth’s surface?

what does the principle of conservation of energy state?

what conclusion can be made from the principle of conservation of energy?

what is an example of conservation of energy?

what is the relationship between work done and resistive forces?

why is initial kinetic energy of a ball not equal to maximum gravitational potential energy when an object stops mid air?

what is power?

w

what are the formulas for power?

what is the rate of doing work equal to?

what is efficiency?

how is efficiency calculated>

what are the formulas for efficiency?