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mixer [17]
3 years ago
13

A subway train accelerates from rest at one station at a rate of 1.50 m/s 2 for half of the distance to the next station, then d

ecelerates at this same rate for the second half of the distance. If the stations are 1200 m apart, find the time of travel (in seconds) between the two stations.
Physics
1 answer:
natali 33 [55]3 years ago
7 0

Answer:

The time of travel between the two stations is 56.6 s.

Explanation:

The equation for the position and velocity of the train will be as follows:

x = x0 + v0 · t + 1/2 · a · t²

v = v0 + a · t

Where

x = position of the train at time t

x0 = initial position

v0 = initial velocity

t = time

a = acceleration

v = velocity at time t

First let´s calculate the time of travel for the first half of the distance:

In this case x0 and v0 = 0. Then:

x =  1/2 · a · t²

600 m = 1/2 · 1.50 m/s² · t²

2 · 600 m /  1.50 m/s² = t²

t = 28.3 s

The velocity at the end of this part of the travel will be:

v = v0 + a · t     (v0 = 0)

v = a · t

v = 1.50 m/s² · 28.3 s = 42.5 m/s

Now, let´s calculate the time for the second half of the travel. The initial velocity will be the final velocity of the first part of the travel (42.5 m/s).

Using the equation for velocity:

v = v0 + a · t

0 m/s = 42.5 m/s - 1.50 m/s² · t

-  42.5 m/s /  - 1.50 m/s² = t

t = 28.3 s

This makes sense because the acceleration is of the same magnitude.

The time of travel between the two stations is (28.3 s + 28.3 s) 56.6 s.

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100 points!!! Please help!!!
Greeley [361]

Answer:

41°

Explanation:

Kinetic energy at bottom = potential energy at top

½ mv² = mgh

½ v² = gh

h = v²/(2g)

h = (2.4 m/s)² / (2 × 9.8 m/s²)

h = 0.294 m

The pendulum rises to a height of  above the bottom.  To determine the angle, we need to use trigonometry (see attached diagram).

L − h = L cos θ

cos θ = (L − h) / L

cos θ = (1.2 − 0.294) / 1.2

θ = 41.0°

Rounded to two significant figures, the pendulum makes a maximum angle of 41° with the vertical.

7 0
4 years ago
The length of a 100 mm bar of metal increases by 0.3 mm when subjected to a temperature rise of 100°C. The coefficient of linear
Juli2301 [7.4K]

Answer:

α = 3×10^-5 K^-1

Explanation:

let ΔL be the change in length of the bar of metal, ΔT be the change in temperature, L be the original length of the metal bar and let α be the coefficient of linear expansion.

then, the coefficient of linear expansion is given by:

α = ΔL/(ΔT×L)

   = (0.3×10^-3)/(100)(100×10^-3)

   = 3×10^-5 K^-1

Therefore, the coefficient of linear expansion is 3×10^-5 K^-1

5 0
4 years ago
A Carnot engine operates with an efficiency of 26.0% when the temperature of its cold reservoir is 281 K. Assuming that the temp
VLD [36.1K]

Answer:

The temperature of cold reservoir should be 246.818 K for efficiency of 35%

Explanation:

In first case we have given efficiency of Carnot engine = 26 % = 0.26

Temperature of cold reservoir T_L=281K

We know that efficiency of Carnot engine is given by

\eta =1-\frac{T_L}{T_H}

0.26 =1-\frac{281}{T_H}

T_H=379.72K

For second Carnot engine efficiency is given as 35% = 0.35

And temperature of hot reservoir is same so T_H=379.72K

So 0.35=1-\frac{T_L}{379.72}

T_L=246.818K

So the temperature of cold reservoir should be 246.818 K for efficiency of 35%

4 0
4 years ago
A magnetically soft material is placed in a strong magnetic field. What is the most likely outcome?
Svet_ta [14]

D-It will become a temporary magnet because the domains will easily realign.

9 0
3 years ago
Read 2 more answers
Fiora starts riding her bike at 20 mi/h. After a while, she slows down to 14 mi/h, and maintains that speed for the rest of the
goblinko [34]

Answer:

3.5 hours

Explanation:

Speed = distance/time

Let the distance that Fiora biked at 20 mi/h through be x miles and the time it took her to bike through that distance be t hours at 20 mi/h

Then, the rest of the distance that she biked at 14 mi/h is (112 - x) miles

And the time she spent biking at 14 mi/h the rest of the distance = (6.5 - t) hours

Her first biking speed = 20 mph = 20 miles/hour

Speed = distance/time

20 = x/t

x = 20 t (eqn 1)

Her second biking speed = 14 mph = 14 miles/hour

14 = (112 - x)/(6.5 - t)

112 - x = 14 (6.5 - t)

112 - x = 91 - 14t (eqn 2)

Substitute for x in (eqn 2)

112 - 20t = 91 - 14t

20t - 14t = 112 - 91

6t = 21

t = 3.5 hours

x = 20t = 20 × 3.5 = 70 miles.

(112 - x) = 112 - 70 = 42 miles

(6.5 - t) = 6.5 - 3.5 = 3 hours

Meaning that she travelled at 20 mi/h for 3.5 hours.

4 0
3 years ago
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