Solving Deceleration Problem: Speed & Time Calculation

  • Thread starter ballerinajen426
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    Deceleration
In summary, the driver of a pick up truck going 100 km/h applies the brakes, giving the truck a uniform deceleration of 6.5m/s(squared) while it travels 20.0 m. Using the formula u^2 = v^2 + 2as, the final speed of the truck is 81.4 km/h. To find the time elapsed, the formula v = u + at can be used, with the final velocity from part a. Showing work when changing units is important to avoid errors.
  • #1
ballerinajen426
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Homework Statement



The driver of a pick up truck going 100 km/h applies the brakes, giving the truck a uniform deceleration of 6.5m/s(squared) while it travels 20.0 m
a) what is the speed of the truck in km/h at the end of tihs distance
b) how much time has elapsed

her is the thing i have the answers but no way of showing my work and with the change in units km/h m/s i get mixed up PLEASE HELP!

answers
a) 81.4 km/h
b) 0.794 s
 
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  • #2
Ok so what would you do first for a)?

what formula would you use to solve for the final speed of the truck?

also I think you need to do b) before you can do a).

so what equation can you use to solve for the time elapsed?

When you're going to change the units just make sure to show your work really good in order to spot an error.

Other than that I don't think I can help you out more without giving the answer away.
Just show some work even if you do it wrong at least we'll see if you are going on the right track and just messed up on units/etc...
 
  • #3
a)
try the formula u^2 = v^2 + 2as
where u=initial velocity, v=final velocity, a=acceleration (will be a negative), and s=the distance traveled.

b)
try using v = u + at
using the final velocity that you found in section a.
t will give you time.
 

1. What is deceleration and why is it important to understand?

Deceleration is the rate of decrease in speed or velocity. It is important to understand because it affects the time it takes to come to a complete stop, which is crucial for safety in various situations, such as driving, sports, and engineering.

2. How do you calculate deceleration?

Deceleration can be calculated by dividing the change in velocity by the change in time. The formula for deceleration is a = (vf - vi) / t, where a is the deceleration, vf is the final velocity, vi is the initial velocity, and t is the time.

3. What is the relationship between deceleration, speed, and time?

The relationship between deceleration, speed, and time can be described by the formula d = v0t + 1/2at^2, where d is the distance traveled, v0 is the initial velocity, t is the time, and a is the deceleration. This formula shows that the deceleration, time, and distance are all directly proportional to each other.

4. How do you solve for speed given deceleration and time?

To solve for speed, use the formula v = v0 + at, where v0 is the initial velocity, a is the deceleration, and t is the time. Simply plug in the given values and solve for v.

5. Can you use deceleration to calculate the time it takes to come to a complete stop?

Yes, you can use deceleration to calculate the time it takes to come to a complete stop. The formula for time is t = (vf - vi) / a, where vf is the final velocity, vi is the initial velocity, and a is the deceleration. By plugging in the given values, you can calculate the time it takes to come to a complete stop.

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