Car Speed After 200m: 31.3m/s

[vaironl]

Homework Statement

A race car starting from rest accelerates uniformly at a rate of $4.90m/s^{2}$ . What is the car's speed after it has traveled 200m?

Homework Equations

Δv = $\frac{Change in position}{change in time}$

The Attempt at a Solution

v=$\sqrt{980m^2/s^2}$

=31.3m/s

 

[SammyS]

Homework Statement

A race car starting from rest accelerates uniformly at a rate of $4.90m/s^{2}$ . What is the car's speed after it has traveled 200m?

Homework Equations

Δv = $\frac{Change in position}{change in time}$

The Attempt at a Solution

v=$\sqrt{980m^2/s^2}$

=31.3m/s

Show your work so that we can help you see where your error is.

How did you get $v=\sqrt{980m^2/s^2}\,?$

 

[gneill]

What kinematic formula are you using? It looks like you've missed out a constant.

 

[vaironl]

Show your work so that we can help you see where your error is.

How did you get $v=\sqrt{980m^2/s^2}\,?$

What kinematic formula are you using? It looks like you've missed out a constant.

Well I'm required to find the speed after 200 meters, but I was never given any time.

So I assume... Which is not a good thing to do, multiplying the acceleration * the distanced travel would give me the speed.

But I really can't remember the actual equation.

 

[gneill]

Well I'm required to find the speed after 200 meters, but I was never given any time.

So I assume... Which is not a good thing to do, multiplying the acceleration * the distanced travel would give me the speed.

But I really can't remember the actual equation.

If you can't remember you should check your notes or textbook! Your formula is close to being a valid kinematic expression,... but it's missing a constant. Do you have a list of the common kinematic expressions?

 

[vaironl]

If you can't remember you should check your notes or textbook! Your formula is close to being a valid kinematic expression,... but it's missing a constant. Do you have a list of the common kinematic expressions?

I have the textbook, and I did have an example sheet but my friend borrowed to check her work. I found this expression which seems to satisfy my problem, v2 = vo2 + 2a(X - Xo)

Therefore V2= 0m/s + 2(4.90m/s^2)(200m)

v2= 9.8m/s^2(200m)
v2= 1960m^2/s^2
v=$\sqrt{1960m^2/s^2}$
v= 44.3m/s

 

[gneill]

I have the textbook, and I did have an example sheet but my friend borrowed to check her work. I found this expression which seems to satisfy my problem, v2 = vo2 + 2a(X - Xo)

Therefore V2= 0m/s + 2(4.90m/s^2)(200m)

v2= 9.8m/s^2(200m)
v2= 1960m^2/s^2
v=$\sqrt{1960m^2/s^2}$
v= 44.3m/s

That looks better