### Topic Content:

- Definition of Speed
- Definition of Velocity
- Definition of Acceleration

### What is Speed?

Speed is the distance covered per time taken or the rate of change of distance. It is a scalar quantityA scalar quantity is a quantity that does not depend on direction. It can also be defined as a quantity with magnitude only. Examples of Scalar Quantities include area, density, distance,... More and measured in km per hour or metre per second (m/s or \( \scriptsize ms^{-1}\)).

Speed = \( \frac {distance}{time} \)

Average Speed = \(\frac{Total \: distance \:covered}{total\:time\: taken} \)

**Uniform Speed: **A body is said to move with uniform speed if the time rate of change in distance is constant.

Speed in \( \frac {km}{hr}\)or km/hr can easily be converted to m/s or ms^{-1}.

This is achieved as follows:

Speed = \( \frac {distance \: in \: km}{time\: in\: hour} = \frac {1km}{1hr} \)

But 1 km = 1000 m, 1 hr = 3600s

Therefore, To convert km/hr to m/s, the conversion factor is

â‡’ \( \frac {1000}{3600} \scriptsize \: \times \: (Speed \: in \: km/h)\; = \: Speed\: in\: ms^{-1} \)

### Example 4.5.1:

**(i)** Convert 36 \( \frac {km}{hr} \) to ms^{-1}

**Solution: **\( \frac {1000}{3600}\scriptsize \times 36 \\ \scriptsize = 10 \: ms^{-1}\)

**(ii)** Convert 72 \( \frac {km}{hr} \) to ms^{-1}

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Highly helpful…

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Great lesson