Help? I'm pretty sure I have it, but not 100%

- BloomLocke367

Help? I'm pretty sure I have it, but not 100%

- jamiebookeater

See more answers at brainly.com

At vero eos et accusamus et iusto odio dignissimos ducimus qui blanditiis praesentium voluptatum deleniti atque corrupti quos dolores et quas molestias excepturi sint occaecati cupiditate non provident, similique sunt in culpa qui officia deserunt mollitia animi, id est laborum et dolorum fuga.
Et harum quidem rerum facilis est et expedita distinctio. Nam libero tempore, cum soluta nobis est eligendi optio cumque nihil impedit quo minus id quod maxime placeat facere possimus, omnis voluptas assumenda est, omnis dolor repellendus.
Itaque earum rerum hic tenetur a sapiente delectus, ut aut reiciendis voluptatibus maiores alias consequatur aut perferendis doloribus asperiores repellat.

Get this expert

answer on brainly

SEE EXPERT ANSWER

Get your **free** account and access **expert** answers to this

and **thousands** of other questions

- BloomLocke367

The highest speed achieved by a standard nonracing sports car is \(3.50\times 10^2~km/hr\). Assuming that the car accelerates at 4.00m/s, how long would it take this car to reach its maximum speed if it is initially at rest? What distance would the car travel during this time?

- BloomLocke367

I for sure have the first question (and work to prove it) but I'm not sure if I need to do one more step on the last question. The units are throwing me off.

- BloomLocke367

@Nnesha, can you help?

Looking for something else?

Not the answer you are looking for? Search for more explanations.

## More answers

- BloomLocke367

- BloomLocke367

Can you help?

- mathmate

Yes, units are the key!

- mathmate

I prefer to work with metres/second, because these are standard / basic units.

- mathmate

so 3.5*10^2 km/hr = 350 km/hr = 350*1000 m / 3600 s. = 875/9 m/s (exact conversion)

- BloomLocke367

The first thing I did was convert km/hr to m/s by doing \(\Huge(\frac{350km}{1hr})(\frac{1hr}{60min})(\frac{1min}{60sec})(\frac{1000m}{1km})\) and I got 97.2m/s

- BloomLocke367

that's with keeping the right amount of significant figures.

- mathmate

Yes, 97.2 m/s is correct to one place after decimal.
I prefer to keep the exact values until the end, if possible.

- mathmate

So what did you get for the time to accelerate?

- BloomLocke367

okay then I used the formula \(v=v_0+at\) and I got 24.3s for the time.

- mathmate

Yep, that's what I got too, 24.306 (if you want to be more precise).
Which kinematics equation would you use to find the distance?

- BloomLocke367

I used \(v^2=v_0^2+2a(x-x_0)\)

- mathmate

That's good! So what do you get with the distance (x-x0)?

- mathmate

The term v^2 will exaggerate the round-off errors, so be sure to keep more significant figures.

- BloomLocke367

welllllll, that's my problem. I got all the way down to my last step where I have to divide \(9447.84m^2/s^2\) and \(8.00m/s^2\). I got lost with the units at this point. I'm not sure what I'm left with after I divided

- mathmate

Units can be manipulated exactly as variables, as you can see below.
In physics (and chemistry), this is a very important technique to keep track of the units (dimensions) of the answer. With some practice, you'll be very good at it.
9447.84m2/s2 / 8.00m/s2
=9447.84 / 8 * (m^2/m) / (s^2/s^2)
=1180.98 m
( I get 1181.52 m if I keep sufficient significant figures).
(gtg, will be back later)

- BloomLocke367

I got the same number and I thought it was only m left but I wanted to be sure I didn't need to take the square root. Thanks for the help :)

- BloomLocke367

wait wait wait. How did you get 1181.52m?

- BloomLocke367

Shouldn't there be only 3 significant fig?

- mathmate

Yes, the answer should give only 3 significant figures.
To make sure the third figure is correct, you would want to carry out your calculations keeping at least 4 or even 5 if there are powers involved. Then round to three for the answer.

- mathmate

By solving
(875/9)^2=0^2+2(4.00)S
S=1181.52...

- BloomLocke367

I got 1180.98... I'm so confused.

- mathmate

94.2^2=9447.84 (rounded too early)
(875/9)^2=9452.16.... (exact)

- mathmate

As I said earlier, whenever a number is raised to a power (like squared), the round-off error is magnified. Squaring will double the round off error.

- BloomLocke367

ohhhhh okay.

Looking for something else?

Not the answer you are looking for? Search for more explanations.