# A boat moves 15 km

ArcherofScience

## Homework Statement

A boat moves 15 km as it accelerates at 3.5 m/s^2 for 1.5 minutes. What is the truck's initial velocity?

## Homework Equations

i'm stuck on what formula to use....

3. The Attempt at a Solution [/]
vf^2=vo^2+2ax? ....

Homework Helper

## Homework Statement

A boat moves 15 km as it accelerates at 3.5 m/s^2 for 1.5 minutes. What is the truck's initial velocity?
What does the truck have to do with the boat?

i'm stuck on what formula to use....

3. The Attempt at a Solution [/]
vf^2=vo^2+2ax? ....

If you are stuck on a formula, draw the v-t diagram.
The boat starts at some speed u at t=0 and increases it's speed to speed v at t=90s.
This gives you a trapezium shape with two unknown points in it.

The slope of the line is the acceleration - which you have been given.
The area under the graph is the distance - which you have been given.
The rest is basic geometry.

(The other approach is to list all the kinematic equations, and list the variables you know. The equation with all the ones you know and the one you want to find is the correct one.)

chief10
You will have to employ your elementary equations of motion in Physics. This question is quite basic. I'm guessing the truck and the boat are the same thing and you just mixed them up.
The SUVAT equation you used is incorrect because you are not given your final velocity so employing v^2=u^2+2as is not helpful because you're just introducing more unknown variables.

Below is the correct method of solving this question if you don't want to sketch a graph. Although it's good to know how to do them.

s (displacement) =15km=15000m
a (acceleration) =3.5
t (time) =1.5mins=90
u (initial velocity)=?

s = u*t+(0.5)at^2

have a go at that, that should do it.