Trying to understand how to make Motion Diagrams

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Homework Help Overview

The discussion revolves around creating motion diagrams in the context of a physics problem involving a car's deceleration when a driver sees a police car. The original poster expresses confusion regarding the accuracy required for the diagrams and how to incorporate the driver's reaction time into the representation of motion.

Discussion Character

  • Exploratory, Assumption checking, Problem interpretation

Approaches and Questions Raised

  • Participants discuss the initial steps for creating a motion diagram, including the importance of accurately representing the initial velocity and the effects of reaction time. Questions are raised about how to visually depict the transition from acceleration to deceleration.

Discussion Status

Some participants have offered guidance on starting the motion diagram by suggesting the use of a graph to represent velocity over time. There is acknowledgment of the complexity introduced by the reaction time, and one participant proposes simplifying the problem by ignoring the reaction time initially.

Contextual Notes

The original poster is navigating their first college physics assignment and is uncertain about the expectations for accuracy in their motion diagrams. The problem involves specific values for speed, acceleration, and reaction time, which are critical to the discussion.

Dko
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Trying to do my first Physics home work assignment for college and I'm not really making any headway. He went thru the martial so fast while throwing in calculus that I'm not sure if I do or don't need.
My main problem with Motion Diagrams is I'm not sure how accurate I'm supposed to be and how do I get that level of accuracy I need?
The problem I'm on bellow, is really getting me because I don't know how to start. Should I show 35 meters of movement and the reaction time before the deceleration?

Homework Statement


"The driver of a car traveling at 35 m/s suddenly sees a police car. The driver attempts to reach the speed limit of 25 m/s by accelerating at 2.5 m/s^2. The driver has a reaction time of 0.55 s. (The reaction time is the time between first seeing the police car and pressing the brake.)

Homework Equations



The Attempt at a Solution


I really don't know how I would show a solution on here.

Hope my problem makes sense.
 
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Dko said:
Trying to do my first Physics home work assignment for college and I'm not really making any headway. He went thru the martial so fast while throwing in calculus that I'm not sure if I do or don't need.
My main problem with Motion Diagrams is I'm not sure how accurate I'm supposed to be and how do I get that level of accuracy I need?
The problem I'm on bellow, is really getting me because I don't know how to start. Should I show 35 meters of movement and the reaction time before the deceleration?

Homework Statement


"The driver of a car traveling at 35 m/s suddenly sees a police car. The driver attempts to reach the speed limit of 25 m/s by accelerating at 2.5 m/s^2. The driver has a reaction time of 0.55 s. (The reaction time is the time between first seeing the police car and pressing the brake.)

Homework Equations



The Attempt at a Solution


I really don't know how I would show a solution on here.

Hope my problem makes sense.

Welcome to the PF.

I would start this problem by drawing a graph with velocity on the vertical axis and time on the horizontal axis. Draw the 35m/s initial velocity starting before time t=0 (to the left of the vertical axis), and then at t=0, that's when he sees the police car. But there is reaction time before he starts decelerating, so the 35m/s line continues for a bit, and then starts decreasing due to the deceleration...
 
I recommend ignoring the reaction time of the driver and just starting by calculating how long it will take for the car to decelerate (or accelerate backwards) from 35 to 25 m/s with the acceleration given in the problem. Do you know how to do that?
edit: If you can do that then move on to berkeman said above.
 
Thanks. I think I have a handle on things now. Youtube helped some as well.
 

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