Calculating Acceleration of a Car After Braking

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SUMMARY

The discussion focuses on calculating the acceleration of a car that decelerates from 95 km/hr to a stop over a distance of 60 meters. The correct formula used is vf^2 = vi^2 + 2ax, where vf is the final velocity (0 m/s), vi is the initial velocity (converted from 95 km/hr to 26.39 m/s), and d is the distance (60 meters). The calculated acceleration is -5.81 m/s², confirming the teacher's answer. The key takeaway is the necessity of unit conversion for accurate calculations in kinematics.

PREREQUISITES
  • Understanding of kinematic equations, specifically vf^2 = vi^2 + 2ax
  • Ability to convert units, particularly from km/hr to m/s
  • Basic knowledge of acceleration and deceleration concepts
  • Familiarity with the concept of initial and final velocity
NEXT STEPS
  • Learn about unit conversion techniques, especially for speed and distance
  • Study additional kinematic equations involving time, such as d = vi*t + 0.5*a*t^2
  • Explore real-world applications of acceleration calculations in automotive engineering
  • Investigate the effects of friction and braking force on vehicle deceleration
USEFUL FOR

Students studying physics, automotive engineers, and anyone interested in understanding the principles of motion and acceleration in vehicles.

IDespisePhysics
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Homework Statement


A car is traveling at 95 km/hr. The driver steps on the brakes and the car comes to a stop in 60 meters. What is the car's acceleration?

Homework Equations


My issue might be which formula is correct but, I believe I would use, vf^2=vi^2+2ax

The Attempt at a Solution


Every time I begin any problem I write down the givens.
d= 60 meters
Vi= 95 km/hr
Vf= 0 m/s
Are my givens wrong? If not, I've continued to plug it in into the problem above. I assume I'm using Kinematics and since the other equations require 't' or time, I don't believe I use those equations for this problem. As I plug the givens into the equation above, the math doesn't add up to the answer my teacher had said it was; which is -5.81m/s^2.
 
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Would I have to convert the 95 km/hr?
 
IDespisePhysics said:
Would I have to convert the 95 km/hr?
That is one of your first steps to convert it out to get similar units.
 
Thank you! I got the answer now! :D
 
IDespisePhysics said:
Thank you! I got the answer now! :D
Happy to help :-)
 

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