Question

4. A driver travels 135 km, east in 1.5 h, stops for 45 minutes for lunch,

and then resumes driving for the next 2.0 h through a displacement
of 215 km, east. What is the driver's average velocity?


An explanation too please

Answer 1

The driver's average velocity is 82.35 km/h.

Step-by-step explanation:

Given:

The motion of the driver can be divided into 3 parts:

i. Displacement of the driver in 1.5 hours = 135 km

ii. Rest for 45 minutes.

iii. Displacement in next 2 hours = 215 km

The direction of motion remains same (east).

Now, total displacement of the driver is,
`D_(Total)=135+215=350` km.

Rest time is 45 minutes. Converting it to hours, we need to use the conversion factor
`1\textrm{ min} = (1)/(60)` hour.

So, 45 minutes in hours is equal to
`(45)/(60)=0.75` hours.

Now, total time taken for the complete journey is,
`\Delta t=1.5+(45)/(60)+2=1.5+0.75+2=4.25\textrm{ h}`

Average velocity is given as:

`v_(avg)=\frac{\textrm{Total displacement}}{Total time}=(350)/(4.25)=82.35\textrm{ km/h}`

Therefore, the driver's average velocity is 82.35 km/h