Instantaneous Velocity: drag racing problem

In summary, the conversation is about solving for the velocity of a funny car at different points in time. The person encountered difficulties with the program used for class, but eventually found the correct answer for t=2 seconds. However, they are struggling to find the correct answer for t=4 seconds, with their tangent line appearing to be off. They are seeking help to figure out what they are doing wrong and how to calculate the slope correctly.
  • #1
chinnie15
29
0
The figure shows a graph of actual position-versus-time data for a particular type of drag racer known as a "funny car."
Physicsproblem2.png


Estimate the car's velocity at 2.0s

Equation:
v = m/s
I thought I knew how to solve this, and I made a tangent line at the curve and 2s, and when I do the slope at different points on the tangent I keep getting somewhere in the field of 50m/s. However, it keeps telling me I'm wrong. What should I be doing differently?

Thank you for your help!
 
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  • #2
your answer looks ok to me. what keeps telling you that its wrong?
 
  • #3
The program I have to use for class (Mastering Physics). It says express the answer with proper units and 2 significant figures, but whether I put in 50m/s or 50.0 m/s, it's still saying it's incorrect?
 
  • #4
chinnie15 said:
The program I have to use for class (Mastering Physics). It says express the answer with proper units and 2 significant figures, but whether I put in 50m/s or 50.0 m/s, it's still saying it's incorrect?
I get a somewhat steeper slope. ≈ 65 m/s

Have you tried entering scientific notation?
 
  • #5
Thanks!

67 m/s ended up being the correct answer. I redrew my tangent line, and took another slope and I ended up getting an answer extremely close to that, so my tangent line was just off before. Only problem is now, I have to do this again for t=4s. I have, once again, exhausted most of my attempts trying to get the correct answer. What am I doing wrong?? Here is my tangent line for t=4:
Physicsproblem22.png


I am getting a slope around 80m/s. Is my tangent line really that off?

Thank you so much for your help!
 
  • #6
chinnie15 said:
Thanks!

67 m/s ended up being the correct answer. I redrew my tangent line, and took another slope and I ended up getting an answer extremely close to that, so my tangent line was just off before. Only problem is now, I have to do this again for t=4s. I have, once again, exhausted most of my attempts trying to get the correct answer. What am I doing wrong?? Here is my tangent line for t=4:
Physicsproblem22.png


I am getting a slope around 80m/s. Is my tangent line really that off?

Thank you so much for your help!
That's at t = 4 seconds !
 
  • #7
I know that. :) This is for the second question, which is for the velocity at t = 4s. The first question was t = 2s. I got that answer for t = 2s correct now, it was 67 m/s. But now I can't get the correct answer for t = 4s.
 
  • #8
chinnie15 said:
I know that. :) This is for the second question, which is for the velocity at t = 4s. The first question was t = 2s. I got that answer for t = 2s correct now, it was 67 m/s. But now I can't get the correct answer for t = 4s.
How do you figure that slope to be 80 ?

It's much more like ≈250/2 = 125
 

What is instantaneous velocity in drag racing?

Instantaneous velocity refers to the velocity of an object at a specific moment in time. In drag racing, this is the speed of a car at a specific point during the race, such as at the starting line or at the finish line.

How is instantaneous velocity calculated in drag racing?

To calculate instantaneous velocity in drag racing, the distance traveled by the car and the time taken to cover that distance must be known. The velocity can then be calculated by dividing the distance by the time. This can be done using a timer and measuring the distance with a measuring tape or by using specialized equipment such as a laser timing system.

What factors affect instantaneous velocity in drag racing?

There are several factors that can affect instantaneous velocity in drag racing, including engine power, aerodynamics of the car, and track conditions. The type of tires, weather conditions, and the driver's skill can also play a role in determining the car's instantaneous velocity.

Why is instantaneous velocity important in drag racing?

Instantaneous velocity is important in drag racing because it allows drivers to monitor their speed and make necessary adjustments during the race. It also helps in determining the car's acceleration and can be used to predict the car's performance in future races.

How does instantaneous velocity differ from average velocity in drag racing?

Instantaneous velocity is the speed of the car at a specific moment in time, whereas average velocity is the total distance traveled divided by the total time taken. Average velocity takes into account the entire race, while instantaneous velocity only focuses on a specific point in the race.

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