Calculating Velocity: Car and Earth in Motion – Help with Velocity Questions

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Homework Help Overview

The discussion revolves around a physics problem involving the calculation of velocities in a scenario where a car is moving and rain is falling. The original poster seeks assistance in understanding how to determine the velocity of the rain with respect to both the car and the earth, given the angles and speeds involved.

Discussion Character

  • Exploratory, Assumption checking, Mathematical reasoning

Approaches and Questions Raised

  • Participants suggest using a right triangle to visualize the problem, specifically a 30-60-90 triangle, to relate the velocities of the car and the rain. There is a focus on the relationship between the velocities and the angles involved, particularly using trigonometric functions.

Discussion Status

Some participants have provided calculations and suggested methods for finding the velocities, indicating a productive exploration of the problem. However, there is no explicit consensus on the final approach or solution, as discussions continue regarding the relationships between the different velocities.

Contextual Notes

The original poster expresses confusion regarding "with respect to" questions, indicating a potential gap in understanding the concepts involved. There is also a mention of the need to clarify the relationship between the velocities and the angles presented in the problem.

arpitm08
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velocity question help?

Homework Statement


A car is going at 50 km/h due east. Water is falling vertically with respect to the earth. Looking at the side windows the water creates a 60 degree angle with the vertical. What is the velocity of the water with respect to
a) car
b) earth.


Homework Equations



I don't know how to solve, so I don't know any relevant equations.

The Attempt at a Solution



Did not know how to approach. Could someone please clear this up for me. These type of "with respect to" questions are really confusing for me.
 
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Draw a 30-60-90 (right) triangle, with the 60 in the upper vertex (angle between hypotenuse and vertical leg).

The car travels a distance 50 km/h*T, and make that the length of the base.

In the same time T, the rain falls distance Vrain*T. Make that the other leg.

What is relationship between Vcar = 50 km/h and Vrain?
 
Astronuc said:
What is relationship between Vcar = 50 km/h and Vrain?

Tan 60 = 50 km/h / Vrain
Vrain=28.87 km/h

So that is the velocity of the rain with respect to the car. Would you just solve for the hypotenuse to get the velocity of the rain with respect to the earth.
 
just use trignometry...
 
The 28.9 km/h is the velocity (speed actually) of the rain (falling).

The hypotenuse would give the apparent velocity of the rain as observed from the car.
 

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