A question answer community on a mission

to share Solutions for all STEM major Problems.

to share Solutions for all STEM major Problems.

Cant find a problem on ToughSTEM?

0

Added Wed, 09 Sep '15

Community

1

Add a Comment

Solutions

0

(a) The subway train must then be accelerating at 1.74 m/s2 for half of the distance, then decelerate at -1.74 m/s2 for the other half.

By v_f^2 = v_i^2 + 2ax

v_f^2 = 0 + 2(1.74 m/s2)(408)

v_f = 37.68 m/s

Note: the distance is halved because it takes half of the total distance to reach the max speed. Then, after this speed is reached the subway needs to start decelerating at the max acceleration because otherwise the subway would either make passengers uncomfortable or miss the stop.

(b) The travel time to go the first half is the same as the travel time to go the second half, because the average velocity (v_f+v_i)/2 is the same.

x = (v_avg)*t

408 m = (v_f + v_i)/2*t

408m = (37.68 m/s + 0)/2 * t

t = 21.66 s

The total time is equal to 2t (Because that was just the calculation for halfway). So the answer is 21.66 * 2 = 43.32 s.

(c) The average speed of the train is equal to total distance covered over total time.

At best, it takes 43.32 seconds to travel the 816 m between stations. Thus, the total distance is 816 meters. The total time is equal to the 43.32 seconds of travel plus the 24 seconds of stopping. 43.32+24 = 67.32 s. So by the average speed formula:

s = x/t = 816m/67.32s = 12.12 m/s

Added Wed, 09 Sep '15

Community

1

Add a Comment

Add Your Solution!

Close

Click here to

Choose An Image

or

Get image from URL

GO

Close

Back

Add Image

Close

What URL would you like to link?

GO

α

β

γ

δ

ϵ

ε

η

ϑ

λ

μ

π

ρ

σ

τ

φ

ψ

ω

Γ

Δ

Θ

Λ

Π

Σ

Φ

Ω

∫

∮

∞

∝

∇

∴

→

↔

⊆

⊂

∀

∃

∈

∉

∪

∩

∅

Copied to Clipboard

Sign Up

to interact with the community. (That's part of how we ensure only good content gets on ToughSTEM)

OR

OR

ToughSTEM is completely free, and its staying that way. Students pay way too much already.

Almost done!

Please **check your email** to finish creating your account!

Welcome to the Club!

Choose a new Display Name

Only letters, numbers, spaces, dashes, and underscores, are allowed. Can not be blank.

Great! You're all set, .

A question answer community on a mission

to share Solutions for all STEM major Problems.

to share Solutions for all STEM major Problems.

Why

The Purpose

The Purpose

How

The Community

The Community

Give Feedback

Tell us suggestions, ideas, and any bugs you find. Help make ToughSTEM even better.