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4 years ago

An insulated lunch bag keeps food warm by

Physics

2 answers:

TiliK225 [7]4 years ago

4 0

slowing the transfer of thermal energy from the food inside the bag to the air outside the bag

Norma-Jean [14]4 years ago

3 0

The answers to the question above are "D) slowing the transfer of thermal energy from the food inside the bag to the air outside the bag" which is how an insulated food bag keeps the food warm. The "insulate" word means "to protect something from losing heat". Thus, the function of the insulated food bag is related to its name.

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1. An express train, traveling at 36 m/s, is accidentally sidetracked onto a local train track. The express engineer spots a loc

Colt1911 [192]

Answer:

(i) 12 seconds

(ii) 216 meters from the initial position

(iii) 132 meters from the initial position

(iv) No

Explanation:

Speed of express train =36 m/s

Speed of local train =11 m/s

The initial distance between the local train and passenger train =100 m.

Due to the application of breaks, the express train slows at the rare of $3.0 m/s^2.$

So, the acceleration of the express train, $a=-3 m/s^2$ .

(i) Let t be the time the express train takes to stop.

From the equation of motion,

v=u+at

where, v: final velocity, u: initial velocity, a: constant acceleration, t: time taken to change the speed from u to v.

In this case, v=0, u=36 m/s, $a=-3 m/s^2$

So, 0=36+(-3)t

$\Rightarrow t= 36/3=12$ seconds.

(ii) To compute the distance traveled, s, till the express train stops, using

$v^2=u^2+2as$

$\Rightarrow 0^2=36^2+2(-3)s$

$\Rightarrow s=\frac{36\times36}{6}$

$\Rightarrow s=216$ meters.

(iii) The local train is moving at a speed of 11 m/s

So, in 12 seconds, the distance, d, traveled by the local train

d= 11x12=132 meters [as distance= speed x time]

(iv) Let 0 be the reference position which is the initial position of the express train.

So, at the initial time, the position of the local train is at 100m.

After 12 seconds:

The position of the express train is at 216 m [using part (ii)]

and the position of the local train is at 100+132=232m [using part (iii)].

So, the local train is still ahead of the express train, hence the trains didn't collide.

6 0

3 years ago

What is the minimum coeffecient of static friction μmin required between the ladder and the ground so that the ladder does not s

mars1129 [50]

Answer:

$\mu = \frac{1}{2tan\theta}$

Explanation:

let the ladder is of mass "m" and standing at an angle with the ground

So here by horizontal force balance we will have

$\mu N_1 = N_2$

by vertical force balance we have

$N_1 = mg$

now by torque balance about contact point on ground we will have

$mg(\frac{L}{2}cos\theta) = N_2(L sin\theta)$

so we will have

$N_2 = \frac{mg}{2tan\theta}$

now from first equation we have

$\mu (mg) = \frac{mg}{2tan\theta}$

$\mu = \frac{1}{2tan\theta}$

3 0

3 years ago

A tall cylinder contains 20 cm of water. Oil is carefully poured into the cylinder, where it floats on top of the water, until t

Zanzabum

Answer:

Pressure, P = 3724 Pa

Explanation:

Given that,

Depth of water, $h_w=20\ cm =0.2\ m$

Depth of oil, $h_o=40-20=20\ cm=0.2\ m$

The density of water, $d_w=1000\ kg/m^3$

The densinty of oil, $d_o=900\ kg/m^3$

We need to find the gauge pressure at the bottom of the cylinder. So, total pressure is equal to :

$P=d_wgh_w+d_ogh_o\\\\P=(d_wh_w+d_oh_o)g\\\\P=(1000\times 0.2+900\times 0.2)\times 9.8\\\\P=3724\ Pa$

So, the gauge pressure at the bottom of the cylinder is 3724 Pa.

3 0

3 years ago

A person is hauling their taco stand and it takes 3,500 Joules of work to stop the taco stand. What force was exerted on the tac

Lapatulllka [165]

Given the work done, the force exerted on the taco stand through the given distance is 2.3 × 10³ Newtons.

Work done is simply defined as the energy transfer that takes place when an object is either pushed or pulled over a certain distance by an external force. It is expressed as;

W = f × d

Where f is force applied and d is distance travelled.

Given that;