Question

3.) A boat is moving south at 15.0, a passenger is walking north along the boat deck at 4.0 and throws a

rock north at 3.0, what is the velocity of the rock when viewed from the boat and the shore? (2)

Answer 1

When viewed from the boat, the velocity of the rock will be equal to the sum of the velocity of the rock relative to the passenger (3.0 m/s north) and the velocity of the passenger relative to the boat (4.0 m/s south).

Therefore, the velocity of the rock when viewed from the boat will be:

Vrock (boat) = Vrock (passenger) + Vpassenger (boat)

Vrock (boat) = 3.0 m/s north + (-4.0 m/s south)

Vrock (boat) = -1.0 m/s south

So, when viewed from the boat, the velocity of the rock will be 1.0 m/s south.

When viewed from the shore, the velocity of the rock will be equal to the velocity of the boat relative to the shore (15.0 m/s south) plus the velocity of the rock relative to the boat (which we calculated as -1.0 m/s south).

Therefore, the velocity of the rock when viewed from the shore will be:

Vrock (shore) = Vrock (boat) + Vboat (shore)

Vrock (shore) = -1.0 m/s south + (-15.0 m/s south)

Vrock (shore) = -16.0 m/s south

So, when viewed from the shore, the velocity of the rock will be 16.0 m/s south.