Kinematics

Question 1

Speed formula,

in words

in symbols

Answer 1

average speed = distance / time

v = d / t

Question 2

Average speed definition

Answer 2

the total distance travelled by an object divided by the total time taken

Question 3

Instantaneous speed definition

Answer 3

the speed of an object measured over a very short period of time

Question 4

SI Unit for speed

Answer 4

ms^-1

Question 5

Displacement definition

Answer 5

the distance travelled in a particular direction; a vector quantity

Question 6

Vector quantities

Answer 6

has both a magnitude (size) and direction

Question 7

Scalar quantities

Answer 7

has only a magnitude (size)

Question 8

Velocity definition

Answer 8

an object’s speed in a particular direction

rate of change of an object’s displacement

Question 9

Velocity formula,

in words

in symbols

Answer 9

change in displacement / time taken

v = s / t

Question 10

Displacement-time graphs;

quantity derived from graph

straight line

slope

slope = 0 (flat line)

positive slope to immediate negative slope

curved

Answer 10

velocity = gradient of displacement-time graph

object at constant velocity

slope can show which object is moving faster, the steeper the slope the greater the velocity

the slope is zero meaning the gradient is zero subsequently the velocity is zero meaning the object is stationary

negative slope implies the object is travelling back in the direction is came, returning to origin

a curved line means the slope is changing hence the velocity is also changing

Question 11

How to find gradient

Answer 11

choose 2 points on the graph and a y value subtracted from the other divided by the first y values x value subtracted from the other

Question 12

Vector diagram with right angle

Answer 12

use the rules of sin cos and tan to solve any missing angles or lengths (quantities)

Question 13

Vector diagram drawn to scale

Answer 13

If the vectors don’t have a right angle draw a scale diagram

a) choose a suitable scale eg 1 cm: 3 km
b) draw a line to represent the first vector (north is at the top of the page)
c) draw a line to represent the second vector using a protractor to get the correct angle
d) to find the final displacement connect the triangle and measure the length of the last line and convert using scale to obtain the displacement

Question 14

Vector triangle definition

Answer 14

a triangle drawn to determine the resultant of 2 vectors

Question 15

Resultant vector

Answer 15

the single vector formed by adding 2 or more vectors

Question 16

Combining vectors

Answer 16

first draw a diagram of the directions of the known vectors and quantities, then to construct the accurate vector diagram the vectors must be drawn head to tail

vectors can also be combined using vector components,
vector A = (Ax, Ay)
vector B = (Bx, By)
vector A + B = (Ax + Bx, Ay + By)

Question 17

Subtracting vectors,

formula

key idea

Answer 17

A - B = A + (-B)

to subtract a vector draw it in the opposite direction

Question 18

Examples of other scalar quantities

Answer 18

mass
density
work
pressure

Question 19

Examples of other vector quantities

Answer 19

force

acceleration