Page 3 - CLASS VII Lesson Notes Forces and Energy

SUBTOPIC: 3.2 SPEED

Key Words: speed, average speed, constant, calculate, m/s, metres, per, second
Understanding Speed
• Speed tells us how fast something is moving.
• It is a measure of how much distance an object travels in a given time.
• The standard unit of speed is metres per second (m/s).
• This means how many metres an object travels in each second.
Example: If a horse is running at 15 m/s, it travels 15 metres every second.
Calculating Speed: To calculate speed, use the formula:
speed= !"#$%&'( '*+(,(-
$".( $%/(
• Distance is how far something travels (usually in metres).
• Time is how long it takes (usually in seconds).
• Speed is the result (in m/s if distance is in metres and time is in seconds).
• Example:
A bus travels 100 m in 20 seconds.
speed=100/20=5 m/s
Formula Triangle: You can remember the three related equations using a triangle:

Cover the value you want to find and use the other two.
Worked Examples
1. Distance from Speed and Time
Marcus cycles at 4 m/s for 60 seconds.
distance=4×60=240 m
2. Time from Distance and Speed
Sofia travels 2100 m at a speed of 35 m/s.
time=2100/35=60 s
3. Different Units
If distance is in km and time is in hours, the speed will be in km/h.
Example:
A plane travels 2500 km in 5 hours.
speed=2500/5=500 km/h
Important Notes
Use m/s unless the question says to use other units.
Show all working and always include units in your final answer.

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