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3 years ago

A substance that undergoes a _____ change is still the same substance after the change. molecular chemical physical atomic

Physics

2 answers:

kirza4 [7]3 years ago

6 0

Answer:

physical change

Explanation:

anastassius [24]3 years ago

3 0

The answer is physical change

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A rain gutter is to be constructed from a metal sheet of width 30 cm by bending up one-third of the sheet on each side through a

GarryVolchara [31]

Answer:

Explanation:

The volume of the water carried will be proportional to the cross-sectional area. The cross-section is a trapezoid with height 10sint, where t represents theta. The top of the trapezoid is 10+(2)(10cost), i.e. 10 + 20cost. The base of the trapezoid is 10.

Area of trapezoid = (average of bases) times (height)

= ([10 + (10 +20cost)] / 2 ) 10 sint

= (10 + 10cost)(10sint)

= 100sint + 100sintcost, call this A(t). You need to maximize. So differentiate and set equal to zero.

dA/dt = -100sin(t)^2+100cos(t)+100cos(t)^2 = 0, divide by 100:

-sin(t)^2 + cos(t) + cos(t)^2 = 0, replace sin^2 by 1-cos^2

2cos(t)^2 + cos(t) - 1 = 0, factor

(1+cos(t))(2cos(t)-1)=0, so

cos(t)=1, t=0 that give a min (zero area) not a max, or

cos(t) = 1/2, so t=60 degrees. This gives the max.

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4 years ago

Why should I care about children in Haiti that are being targeted by Haitian gangs?

Colt1911 [192]

Answer:

you don't have to its your choice whether you want to or not.

Explanation:

but you can not leave the fact that there dieing

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3 years ago

13. What type of lens bends light outwards and away from a point?<br> concave

mezya [45]

Answer:

No,it isn't concave. The correct answer is convex lens.

Explanation:

<em>A lens is a piece of transparent material bound by two surfaces of which at least one is curved. A lens bound by two spherical surfaces bulging outwards is called a bi-convex lens or simply a convex lens. A single piece of glass that curves outward and converges the light incident on it is also called a convex lens.</em>

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3 years ago

Read 2 more answers

The air that flows over the top part of an airplane's wing moves faster than the air that flows across the bottom. This faster m

kaheart [24]

As an airplane moves through the air, its wings cause changes in the speed and pressure of the air moving past them. These changes result in the upward force called lift.

The Bernoulli principle states that an increase in the speed of a fluid occurs simultaneously with a decrease in the pressure exerted by the fluid.

A wing is shaped and tilted so the air moving over it moves faster than the air moving under it. As air speeds up, its pressure goes down. So the faster-moving air above exerts less pressure on the wing than the slower-moving air below. The result is an upward push on the wing—lift!

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4 years ago

A car goes from rest to a speed of 90 km/h in 10 seconds . What is the car's acceleration in m/s²

zloy xaker [14]

First you must convert Km/hr to m/s. 90 km/hr equals 25m/s (this can be done through a conversion table by plugging in the conversion values). Then you need to see what was given:
vi (initial velocity)= 0m/s
vf (final velocity= 25m/s (90km/hr)
t (time)= 10s

Next you should find an equation that requires only the values you know and gives you the value you're looking for. Sometimes that requires two equations to be used, but in this case you only need one. The best equation for this would be a=(vf-vi)/t. Finally, plug in your values (a=(25-0)/10) to get your answer which would be 2.5m/s^2. Hope this helped!

7 0

3 years ago