Question

If a boat moves toward north at 10.0 km/hr relative to the river, while the speed of the river current is 5.0 km/hr to the south, what is the actual speed of the boat from an observer on the river bank?

Answer 1

Resultant speed=10-5=5 km/hr
As the boat is at 5 km/hr the actual speed is 5km/hr

Answer 2

Absolute Speed Va = 5.0 km/h (North)

Step-by-step explanation:

Velocity addition rule:

"In classical mechanics, the absolute velocity of a point is equal to the vector sum of its relative and translational velocities".

`\Vec{V_a}= \Vec{V_r}+\Vec{Ve}\\`

Given:

Vr = 10.0 km/h - relative speed (North)

Ve = 5.0 km/h - carrying speed (South)

___________________

Va - ? - Absolute Speed

Va = Vr (North) - Ve (South);

Va = 10.0 - 5.0 = 5.0 km/h (North)