Anti-derivative motion problem

[htoor9]

Homework Statement

The State cycle program requires motorcycle riders to be able to brake from 30 mph(44ft/sec) to 0 in 45 feet. What constant deceleration does it take to do that? No physics formulas allowed.

Homework Equations

Integral rules and whatnot

The Attempt at a Solution

I think v(t) = 44t + V0 but I don't know. I'm just really stumped

 

[Mark44]

Homework Statement

The State cycle program requires motorcycle riders to be able to brake from 30 mph(44ft/sec) to 0 in 45 feet. What constant deceleration does it take to do that? No physics formulas allowed.

Homework Equations

Integral rules and whatnot

The Attempt at a Solution

I think v(t) = 44t + V0 but I don't know. I'm just really stumped

If the equation is v(t) = 44t + v_0, the motorcyclist will be speeding up, not slowing down.

What you have is
\frac{d^2 s}{dt^2} = - a
where a is a positive constant, and v(0) = 44 (ft/sec). You can define s(0) however you want, just so that s(final) is 45 feet away.

 

[htoor9]

If the equation is v(t) = 44t + v_0, the motorcyclist will be speeding up, not slowing down.

What you have is
\frac{d^2 s}{dt^2} = - a
where a is a positive constant, and v(0) = 44 (ft/sec). You can define s(0) however you want, just so that s(final) is 45 feet away.

so if the derivative is going to be -a then v(t) = -44t + v0?

 

[CompuChip]

Does that give you 44 ft/sec if you plug in t = 0?
What is v0?

 

[htoor9]

Does that give you 44 ft/sec if you plug in t = 0?
What is v0?

Ok so it would be v(t) = -at + 44...anyways I ahead and tried to solve the problem. Could anyone check my solution? He said to leave it in fraction form and I got a = 1936/90 or 968/45.

 

[htoor9]

anyone? does 21.5 deceleration make sense as an answer?