Deck 3: Speed, Graphs & Significant Figures

Speed

Distance travelled per unit time.

Average Speed Formula

Average Speed = Total Distance ÷ Total Time.

SI Unit of Speed

metre per second (m/s).

Other Unit of Speed

kilometre per hour (km/h).

Average Speed

Total distance travelled divided by the total time taken.

Instantaneous Speed

Speed at a specific moment.

Speedometer

Measures instantaneous speed.

Convert m/s to km/h

Multiply by 3.6.

Convert km/h to m/s

Divide by 3.6.

Methods of Measuring Speed

Stopwatch and distance, speedometer, and video motion analysis.

Video Motion Analysis

A method of measuring speed by analysing motion frame by frame using videos.

Distance-Time Graph (Horizontal Line)

Object is stationary.

Distance-Time Graph (Straight Line)

Object moves at constant speed.

Distance-Time Graph (Curve)

Object moves at changing (non-uniform) speed.

Gradient of a Distance-Time Graph

Represents the speed of the object.

Steeper Distance-Time Graph

Means the object is moving faster.

Speed-Time Graph (Horizontal Line)

Object moves at constant speed.

Speed-Time Graph (Upward Slope)

Object is accelerating (speed increasing).

Speed-Time Graph (Downward Slope)

Object is decelerating (speed decreasing).

Speed-Time Graph (On x-axis)

Object is stationary (speed = 0).

Speed-Time Graph

Instantaneous speed is read directly from the graph.

Significant Figures

Digits in a number that contribute to its precision.

Non-zero Digits

All non-zero digits are significant.

Zeros Between Non-zero Digits

Zeros between non-zero digits are significant.

Leading Zeros

Leading zeros are not significant.

Trailing Zeros

Trailing zeros are significant only if there is a decimal point.

Multiplication & Division (Significant Figures)

Round the answer to the same number of significant figures as the value with the fewest significant figures.

Addition & Subtraction (Significant Figures)

Round the answer to the same number of decimal places as the value with the fewest decimal places.