Question

Kiley went 5.7 km/h north and then went 5.8 km/h west. From start to finish, she went 8.1 km/h northwest.

Answer 1

Explanation :

Instantaneous velocity: It is defined as the velocity at a particular instant of time.

Average velocity is the ratio of total displacement covered by an object divided by the total time taken.

It is given that, Kiley went 5.7 km/h north and then went 5.8 km/h west. Here, both direction as well as magnitude of velocity is given. This implies the instantaneous speeds.

The resultant of these two velocities would be :

$v=\sqrt{ (v_N)^2+(-v_w)^2$

$v=\sqrt{(5.8\ km/h)^2+(5.7\ km/h)^2}$

$v=8.1\ km/h$

She went 8.1 km/h northwards. This implies resultant velocity i.e. average speed.

So, the correct option is (a).

Hence, this is the required solution.

Answer 2

5.7 km/h north and 5.8 km/h west are instantaneous velocities, while 8.1 km/h is the average velocity.

This is because each value has a magnitude and direction so it is a velocity. Moreover, the 8.1 km/h is the resultant of the two velocities so it is the average while the other two are instantaneous.