Is My Calculation for Car Deceleration Speed Correct?

In summary, the conversation discusses the correct method for calculating deceleration when braking from a speed of 100km/h and a braking distance of 45.73m. The formula used is v^2 = u^2 + 2as, with the units converted to m/s for accuracy. It is mentioned that the deceleration rate of a car in real-world situations is not steady and increases as the speed drops.
  • #1
nic_nic344
2
0
Hey,
Just wanted to clarify that this was the right way to calculate the deceleration when braking from a speed of 100km/h when the braking distance of the car is 45.73m.

I am just using the formula v^2 = u^2 + 2as

Which i have rearranged to find a...

a = (v^2 - u^2)/2s ---------------- s = distance

And I converted the 100km/h to m/s
so...

a = (0 - 27^2) / 2 * 45.73
a = - 7.97ms/s

Is that right?

Or should I just leave the 100 in km...

and then by deceleration is like -100ms/s?

Thanks!
 
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  • #2
Welcome to PF!

nic_nic344 said:
Hey,
Just wanted to clarify that this was the right way to calculate the deceleration when braking from a speed of 100km/h when the braking distance of the car is 45.73m.

I am just using the formula v^2 = u^2 + 2as

Which i have rearranged to find a...

a = (v^2 - u^2)/2s ---------------- s = distance

And I converted the 100km/h to m/s
so...

a = (0 - 27^2) / 2 * 45.73
a = - 7.97ms/s

Is that right?

Or should I just leave the 100 in km...

Hi nic_nic344! Welcome to PF! :smile:

Yes that's right … you get everything into the same units … except that your 27 isn't accurate enough. :wink:
 
  • #3
Hey,
Yeh I will change the units to something like .78
Thanks for your help!
:)
 
  • #4
real world the deceleration rate of a car is not steady state over the speed drop
it starts low and gets higher as speed drops
 

1. What is car deceleration speed?

Car deceleration speed refers to the rate at which a car slows down or decreases its speed. It is typically measured in meters per second squared (m/s^2) or kilometers per hour per second (km/h/s).

2. How is car deceleration speed calculated?

Car deceleration speed can be calculated by dividing the change in the car's velocity by the time it takes to make that change. This can be represented by the formula: deceleration speed = (final velocity - initial velocity) / time. It is important to note that this calculation assumes constant deceleration.

3. What factors affect car deceleration speed?

There are several factors that can affect car deceleration speed, including the car's weight, friction between the tires and the road, braking force, and the condition of the brakes. Other external factors such as road conditions, weather, and air resistance can also impact deceleration speed.

4. How does car deceleration speed affect stopping distance?

The higher the deceleration speed, the shorter the stopping distance will be. This is because a car with a higher deceleration speed will slow down faster, reducing the distance it travels before coming to a complete stop. However, other factors such as reaction time and braking distance also play a role in determining stopping distance.

5. Can car deceleration speed be increased?

Yes, car deceleration speed can be increased by increasing the braking force, improving the condition of the brakes, and reducing the weight of the car. However, it is important to ensure that the deceleration speed is within safe limits to avoid skidding or losing control of the vehicle.

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