## Question

A long distance runner is running at a constant speed of 5 m/s. How long does it take the runner to travel 1 km.

## Answer

**It will take the runner 200 s to travel 1 km.**

## Explanation

**Data:** The information from the question

The runner has a constant speed, s = 5 m/s

Distance covered by the runner, x = 1 km

By converting kilometre to metre, we will have our distance (x) as:

1 km = 1000 m

Thus, distance, x = 1000 m

**Unknown: ** The information we need to find from the question

The time it takes the runner to travel 1 km, t = ?

**Formula:** The equation that will help us to solve the problem

We already know that speed (s) = distance (x) / time (t)

Since we are looking for time, we will make t subject of the formula:

t = x / s [This is the equation that will help us to solve the problem]

### Solution

**First (simple) Method:** In second

Applying t=x/s, we will have:

Time, t = x / s = 1000 m / 5 ms^{-1} = 200 s

**Therefore, it will take the runner 200 seconds to travel 1 kilometre.**

**Second (alternative) Method**: In hour

Since we already have our distance x = 1 km

Our speed, s = 5 m/s

We can convert the above speed into kilometres per hour (km/h) by following the method below:

Since the speed s = 5 m/s and 1 m/s = 3.6 km/h

We can equally say that s = 5 m/s = 5 (3.6 km/h) = 18 km/h

In kilometres, the speed, s = 18 kilometres per hour

Now, to find time, t = x / s = (1 km) / (18 kmh^{-1}) = 0.06 hours.

**Therefore, it will take the runner 0.06 hours to travel 1 km. **

Check University Physics and Fundamentals of Physics for more examples.

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