Newton's Second Law: Solving for Acceleration and Velocity | Homework Help

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Homework Help Overview

The discussion revolves around applying Newton's Second Law to a problem involving acceleration and velocity, particularly in the context of forces acting on an object, including braking forces and air resistance.

Discussion Character

  • Exploratory, Conceptual clarification, Mathematical reasoning

Approaches and Questions Raised

  • Participants explore the relationship between force, mass, and acceleration, with one attempting to set up a differential equation for the motion. Questions arise regarding initial conditions and the interpretation of variables such as speed at time t=0.

Discussion Status

The discussion is active, with participants seeking clarification on initial conditions and the implications of their assumptions. Some guidance has been offered regarding the focus on finding velocity as a function of time rather than a constant.

Contextual Notes

There is mention of specific values and conditions, such as an initial speed of 15 and the nature of the forces involved, but the exact values for parameters like k are not provided, leading to some uncertainty in the discussion.

lauraosborn
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Homework Statement


http://postimage.org/image/810vdcuvf/


Homework Equations



F=ma

The Attempt at a Solution



for part a) i put mdv/dt = -F(brake) - kv

but is lost for what to put in for part b), help?
 
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What is v at t = 0?
 
Doc Al said:
What is v at t = 0?

for part b) am i right if i say that

-the speed is 15 when t=0
-the speed is decreasing
 
lauraosborn said:
for part b) am i right if i say that

-the speed is 15 when t=0
-the speed is decreasing
The first is what I would call the initial condition.
 
c) 1200 dv/dt = -(3600 + kv)
1/(3600+kv) dv = -1/1200 dt

so do i integrate the above equation to find k?
 
You're not finding k (I assume that k is given in your model of air resistance), but v(t).
 

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