A traffic helicopter is flying with an average speed of 144 km/h over a traffic jam onat which the cars move?
the motorway. It takes 7.5 minutes flying in the direction of traffic and 6.5 minutes in
the opposite direction. What is the length of the traffic jam and the average velocity
so relative velocity = distance/60 km/s
518400-velocity of cars =distance/60 km/s
When the helicopter is moving the same direction as the traffic its speed relative to the traffic is helicopter minus traffic speed. When it is moving in the opposite direction as traffic its speed relative to the traffic is helicopter plus traffic. A similar but easier to visualize situation is a boat moving on a river. When it goes against the current you subtract the rivers speed, but when it moves with the current you add their velocities.