Linear kinematics

Question 1

what are the 2 forms of motion?

Answer 1

• Translation (linear motion):
▫ All parts of the body travel exactly the same distance, in exactly the same direction, in the same time

• Rotation (angular motion):
▫ The body moves along a circular path about a line/axis in space so that all parts of the body travel through the same angle, in the same direction, in the same time

• Bodies generally move with a combination of translation and rotation

Question 2

to find out displacement you use?

Answer 2

square root ((A2)(B2)

Question 3

what are speed and velocity and how are they calculated?

Answer 3

• Speed
▫ The rate at which a body moves from its initial location to its
final location along its path of travel
 How far the body goes per unit of time

 Average speed = distance/Δ time
(Δ = change in)

• Velocity
▫ The rate at which a body moves from its initial location to its final location along the straight line joining the two locations taking into account its direction of travel

 Average velocity = Δ displacement/Δ time

Question 4

what is acceleration and how is it calculated?

Answer 4

• Acceleration
▫ The rate at which the velocity of the body changes with respect to time, taking in to account the direction in which velocity is changing

▫ Average acceleration = final velocity – initial velocity/Δtime

▫ Final velocity is often denoted as v or vf

▫ Initial velocity is often denoted as u or vi

Question 5

what is acceleration due to gravity?

Answer 5

• Gravity is the attractive influence (i.e. force) which
the Earth has on bodies close to its surface

• The acceleration due to gravity (typically denoted ‘g’) is a constant value of 9.81 m/s2 towards the centre of the Earth

• Defining positive and negative accelerations can be very tricky
▫ Typically easiest to define the same positive direction for all kinematic variables
▫ Usually upwards and to the right