# Kinematics Problem: Speed of Current, Velocity, Direction

• ellusion
In summary: If you could determine the crossing time for either case, you would know the current's velocity.In summary, a swimmer with a speed of 0.8 m/s in still water crosses a river 86m wide and lands 54m downstream from the starting point. To determine the speed of the current, one can use the formula v=d/t and plug in the distance of 54m and the crossing time of 107.5s. This results in a current velocity of 0.50m/s. Additionally, if the swimmer were to move directly across the river, his heading would be upstream and this would affect his crossing time.
ellusion
A swimmer who can swim at a speed of 0.8 m/s in still water heads directly across a river 86m wide. the swimmer lands at a position on the far bank 54m downstream from the starting point. determine:

a) the speed of the current
b) velocity of swimmer relative to the shore
c) the direction of departure that would have taken the swimmer directly across river

so far i drew myself a picture and found the distance he covered and the time it took him. from there I am just stuck, how do i find the speed of the current.

ellusion said:
A swimmer who can swim at a speed of 0.8 m/s in still water heads directly across a river 86m wide. the swimmer lands at a position on the far bank 54m downstream from the starting point. determine:

a) the speed of the current
b) velocity of swimmer relative to the shore
c) the direction of departure that would have taken the swimmer directly across river

so far i drew myself a picture and found the distance he covered and the time it took him. from there I am just stuck, how do i find the speed of the current.
How far down the stream (a component of his total distance--be careful) did the current move him (displacement) and how long did it take to displace him that distance?

the current moved him 54m down the stream hwo would i get the time

what do you mean by a component of his total distance?

Last edited:
if he were to swim across and there is no current his time would be 107.5s
so could i just plug that to find the velocity of the current
v=d/t
= 54/107.5
=0.50m/s

can i do that

ellusion said:
if he were to swim across and there is no current his time would be 107.5s
so could i just plug that to find the velocity of the current
v=d/t
= 54/107.5
=0.50m/s

can i do that
Yes. Since the swimmer is heading directly across the river, his crossing time is unaffected by the current. If he swam so that he moved directly across the river, his heading would be upstream and that would change his crossing time.

## What is kinematics?

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

## What is the difference between speed and velocity?

Speed is a measure of how fast an object is moving, while velocity is a measure of both the speed and direction of an object's motion.

## How do you calculate the speed of a current?

The speed of a current can be calculated by measuring the distance a floating object travels in a certain amount of time, and then dividing that distance by the time it took for the object to travel it.

## What factors can affect the speed of a current?

The speed of a current can be affected by the density and viscosity of the fluid, the shape and size of the channel, and any obstacles or obstructions in the flow.

## How do you determine the direction of a current?

The direction of a current can be determined by observing the direction in which floating objects move, or by using a flow meter which measures the direction and speed of the current.

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