Question

A person drives for 1.00 h at 10.0 km/h and 2.00 h at 20.0 km/h. What is their average speed, in SI units?

Answer 1

`\begin{gathered} Speed_(average)=16.67(km)/(h) \\ Speed=4.63\text{ }(m)/(s) \end{gathered}`

Step-by-step explanation

Average speed is defined as the total distance travelled by the time taken

`\begin{gathered} Speed_(average)=\frac{total\text{ distance}}{\text{total time}} \\ \end{gathered}`

Step 1

find the total distance

`\text{distance =sp}eed\cdot time`

hence:

a)distance 1

1.00 h at 10.0 km/h

b) distance 2

2.00 h at 20.0 km/h.

so, the total distance is

`\begin{gathered} \text{total distance = 10 km+40 km} \\ \text{total distance =}50\text{ km} \end{gathered}`

Step 2

Now, let

total distance = 50 km

total time= 1 hour+2 hours= 3 hours

replace in the formula

`\begin{gathered} Speed_(average)=\frac{total\text{ distance}}{\text{total time}} \\ Speed_(average)=\frac{50\text{ km}}{3\text{ hours}} \\ Speed_(average)=16.67\text{ km per hour} \end{gathered}`

Step 3

finally, let the answer is SI units:

the units of speed is meter per second or km per hour, so let's convert it

I hope this helps you