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Forces and Motion - Calculating Speed

Grade 6IGCSE

Review the key concepts, formulae, and examples before starting your quiz.

🔑Concepts

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Speed is a measure of how fast an object is moving and is defined as the distance traveled per unit of time.

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The standard International System of Units (SI) unit for speed is meters per second (m/sm/s), but kilometers per hour (km/hkm/h) is also commonly used.

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Average speed is the total distance traveled divided by the total time taken: Average Speed=Total DistanceTotal TimeAverage\ Speed = \frac{Total\ Distance}{Total\ Time}.

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On a Distance-Time graph, the gradient (slope) of the line represents the speed of the object. A steeper line indicates a higher speed.

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A horizontal line on a Distance-Time graph represents that the object is stationary, meaning its speed is 0 m/s0\ m/s.

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To convert from km/hkm/h to m/sm/s, you divide by 3.63.6.

📐Formulae

Speed(v)=Distance(d)Time(t)Speed (v) = \frac{Distance (d)}{Time (t)}

Distance(d)=Speed(v)×Time(t)Distance (d) = Speed (v) \times Time (t)

Time(t)=Distance(d)Speed(v)Time (t) = \frac{Distance (d)}{Speed (v)}

💡Examples

Problem 1:

A toy car travels a distance of 2525 meters in 55 seconds. Calculate the average speed of the car.

Solution:

v=25 m5 s=5 m/sv = \frac{25\ m}{5\ s} = 5\ m/s

Explanation:

To find the speed, we use the formula v=dtv = \frac{d}{t}. Dividing the distance (25 m25\ m) by the time (5 s5\ s) gives the speed of 5 m/s5\ m/s.

Problem 2:

A cyclist travels at a constant speed of 8 m/s8\ m/s for 11 minute. How far does the cyclist travel?

Solution:

d=8 m/s×60 s=480 md = 8\ m/s \times 60\ s = 480\ m

Explanation:

First, convert the time from minutes to seconds: 1 minute=60 seconds1\ minute = 60\ seconds. Then, use the formula d=v×td = v \times t to calculate the distance.

Problem 3:

An airplane travels 1800 km1800\ km at an average speed of 600 km/h600\ km/h. How long does the flight take?

Solution:

t=1800 km600 km/h=3 hourst = \frac{1800\ km}{600\ km/h} = 3\ hours

Explanation:

To find the time, we rearrange the speed formula to t=dvt = \frac{d}{v}. Dividing 1800 km1800\ km by 600 km/h600\ km/h results in a duration of 3 hours3\ hours.

Calculating Speed - Revision Notes & Key Formulas | IGCSE Grade 6 Science