# Velocity/displacement problem

## Homework Statement

For each function, find an expression for the velocity and the value of the displacement and velocity at t=5. Displacement is in metres and time is in seconds.

## Homework Equations

A)[/B] s(t) = 3t + 7

B) s(t) = t3 - 2t2 + 4t - 1

## The Attempt at a Solution

A) [/B]s(t) = 3t + 7
s(5) = 3(5) + 7
= 22 m/s

B) s(t) = t3 - 2t2 + 4t - 1
s(5) = 53 - 2(5) + 4(5) - 1
=94 m/s

SteamKing
Staff Emeritus
Science Advisor
Homework Helper

## Homework Statement

For each function, find an expression for the velocity and the value of the displacement and velocity at t=5. Displacement is in metres and time is in seconds.

## Homework Equations

A)[/B] s(t) = 3t + 7

B) s(t) = t3 - 2t2 + 4t - 1

## The Attempt at a Solution

A) [/B]s(t) = 3t + 7
s(5) = 3(5) + 7
= 22 m/s

B) s(t) = t3 - 2t2 + 4t - 1
s(5) = 53 - 2(5) + 4(5) - 1
=94 m/s
s usually denotes position or displacement, not velocity. How do you find velocity from displacement?

Remember, the problem is asking you to find both displacement and velocity at a given time, t.

Hint: You posted this problem in the Calculus HW forum, yet you used no calculus. Didn't you find that a little odd?