# Kinematics Question: A motorboat and a log in a stream

• dudu
In summary, kinematics is the study of motion, specifically the position, velocity, and acceleration of objects without considering the forces that cause the motion. Speed and velocity are similar concepts, but velocity includes the direction of motion while speed does not. Acceleration is calculated by dividing the change in an object's velocity by the time it takes for that change to occur. Average velocity is the total displacement divided by the total time, while instantaneous velocity is the velocity at a specific moment in time. A motorboat's motion in a stream is affected by both the speed of the boat and the speed of the water, while a log's motion is only affected by the speed of the water.
dudu
Homework Statement
A river flows with a uniform velocity v. A person in a motorboat travels 1.9km upstream, at which time she passes a log floating by. Always with the same throttle setting, the boater continues to travel upstream for another 60.8min and then returns downstream to her starting point, which she reaches just as the same log does. Calculate the velocity of the river.
Relevant Equations
listed below
I found vlog=1.9/t and vb-v=1.15/t and vb+v=d+1.15/60.8 don't know what to do now

What is the purpose of the log, do you think?

have you considered trying to solve the question in the reference frame of the river?

PeroK
Welcome, dudu!

Could you verfy that no originally provided information is missing?
Where that 1.15 and that d and v come from?

## 1. What is kinematics?

Kinematics is the branch of physics that studies the motion of objects without considering the forces that cause the motion.

## 2. What is the difference between speed and velocity?

Speed is the rate at which an object moves, while velocity is the rate at which an object moves in a specific direction. Velocity takes into account both speed and direction.

## 3. How do you calculate average speed?

Average speed is calculated by dividing the total distance traveled by the total time taken.

## 4. How does the motorboat's speed affect the log's position in the stream?

The motorboat's speed will affect the log's position in the stream because the log will be carried along by the current of the stream, but the motorboat's speed will determine how quickly the log moves in relation to the motorboat.

## 5. What is the equation for calculating acceleration?

The equation for calculating acceleration is a = (vf - vi) / t, where a is acceleration, vf is final velocity, vi is initial velocity, and t is time.

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