# Speed and velocity numerical for class 9

This tutorial on Speed and velocity numerical is for class 9 physics students of CBSE and ICSE boards. This also covers **AS Physics** Kinematics (motion).

**Equations for velocity**

There are three ways in which the equation for velocity v = s/t can be rearranged, depending on which quantity we want to determine. **Here, v denotes velocity, s is displacement, and t is time.**

velocity v = s/t = displacement/time

displacement s = v x t = velocity x time

time t = s/v = displacement/velocity

**Equations for speed**

Note also that we can, of course, use the same equations to find speed and distance. **Here, v denotes speed, s is distance, and t is time.**

speed v = s/t = distance/time

distance s = v x t = speed x time

time t = s/v = distance/speed

**Speed and velocity numerical** problems

1 ) **A car is traveling at 15 m s-1. How far will it travel in 1 hour?**

Solution:

v = 15 m/s

t = 1 h = 3600s

distance traveled = s = ?

Choose the appropriate version of the equation and substitute in the values; include units:

s =v t =15m/s x 3600 s = 54000 m = 54 km

The car will travel 54 km in 1 hour.

**2) The Earth orbits the Sun at a distance of 150000000 km: How long does it take light from the Sun to reach the Earth? (Speed of light in space = 3 x 10^8 m/s.)**

Solution:

v = 3 x 10^8 m/s

s = 150000000 km = 150000000000 m = 1.5 x 10^11 m

t = s/v= (1.5 x 10^11)/( 3 x 10^8) seconds = 500 seconds

Light takes 500 seconds to travel from the Sun to the Earth.