- #1

Medgirl314

- 561

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## Homework Statement

A sailboat in a race is moving at 2.5 m/s when it crosses the starting line. It begins to accelerate at 1.1 m/s^2. How long does is take to travel 80m past the starting line?

## Homework Equations

vavg=(vfinal+vinitial)/2

t=x/vavg

v^2=vinital+2aΔx

## The Attempt at a Solution

First I listed all the data I know, stated directly or indirectly in the passage:

a=1.1 m/s

x=80m

vinital=2.5 m/s

Then I used this formula to find the final velocity:

v^2=vinital+2aΔx

v^2=2.5^2 m/s(1.1 m/s^2)*80 m

v^2=2.5^2 m/s (2.2 m/s^2)*80 m

v^2=182.25 m^2/s^2

v=13.5 m/s

Next I found the average velocity:

vavg=(vinital+vfinal)/2

vavg=(2.5+13.5)/2

vavg=8

Finally I found the time:

t=x/vavg

t= 80m/8 m/s

t=8s

Could someone please confirm(or deny) that the time is 8s? I'm somewhat new to the physics world and like to use every resource possible to keep up my GPA. Thank you in advance!

## Homework Statement

Many modern cars are designed so hat the front and the back of the car will collapse before the passenger compartment collapses. This allows the front and back of the car to absorb the impact from a collision while making injury to the passenger less likely or less severe. Supposse a car is traveling at 40 mi/h when the driver runs off the roaf and strikes a large tree. The front of the car collapses and the driver comes to a stop ovet a distance of 0.75 m. Find the acceleration of the driver in m/s^2. Also, convert your answer to g's, where 1g=9.8m/s^2

## Homework Equations

v^2+2aΔx

## The Attempt at a Solution

I started by listing known information:

vinital=40 mi/h

vfinal=0

x=0.75 m

1g=9.8m/s^2

Then I plugged the information into my equation:

v^2=v0^2+2aΔx

0=1600+2a(0.75)

0=400=2a(0.74)

0=400+2a(0.75)

0+533.3{repating 3}(0.75)

a=533.3m/s^2

Then, converting to gs:

a=533.3m/s^2/9.8m/s^2

a=54.42g

Again, would someone please confirm or deny this?

For whatever reason I am not so sure of this answer.