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3 years ago

Please Help! Will mark Brainliest! 100 Points!

2 answers:

8 0

Question 1 - A hand span

Question 2 - B loaf of bread and a pillow

Question 3 - B He should repeat the test with three additional batteries of varying voltages to demonstrate the reproducibility of results.

These questions are all about materials all materials are matter the first question I pick A because a hand span would be a good measuring tool when you are measuring wings like that the second question I pick B because density is how light a object is the third question I pick B because when you repeat the expierment you are adding in the results and making your solution stronger.

Your answers are A,B,and B.

Otrada [13]3 years ago

3 0

C.

A loaf of bread.

D.

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mixas84 [53]

Answer:

Correct answer: The fourth claim

Explanation:

No claim is most accurate but if you have to choose the best from the bad one, it's fourth - Its height decreased as its motion increased.

The potential energy depends from height Ep = m g h and kinetic

energy depends besides mass from velocity (motion) Ek = m v²/ 2

God is with you!!!

8 0

3 years ago

(d) If η = 40% and TH = 427°C, what is TC, in °C?

Brrunno [24]

Answer:

$T_C=256.2^{\circ}C$

Explanation:

Given that,

Efficiency of heat engine, $\eta=40\%=0.4$

Temperature of hot source, $T_H=427^{\circ}C$

We need to find the temperature of cold sink i.e. $T_C$ . The efficiency of heat engine is given by :

$\eta=1-\dfrac{T_C}{T_H}$

$T_C=(1-\eta)T_H$

$T_C=(1-0.4)\times 427$

$T_C=256.2^{\circ}C$

So, the temperature of the cold sink is 256.2°C. Hence, this is the required solution.

3 0

3 years ago

A projectile is shot horizontally at 23.4 m/s from the roof of a building 55.0 m tall. What is the time necessary for the projec

baherus [9]

The horizontal speed has no effect on the answer.

It doesn't matter whether you flick a marble horizontally from the roof,
fire a high-power rifle horizontally from the roof, drive a school bus straight
off the roof, or drop a bowling ball from the roof with zero horizontal speed.
Their vertical speed is completely determined by gravity, (and it happens to
be the same for all of them).

Handy dandy formula for the distance covered by anything that starts out
with zero speed and accelerates to the end:

      Distance = (1/2) (acceleration) x (time)²

If the beginning of the journey is on Earth, then the acceleration is
9.8 m/s² ... the acceleration of gravity on Earth. We'll assume that
the 55-meter rooftop in the question is part of a building on Earth.

   55 meters = (1/2) (9.8 m/s²) x (time)²

Divide each side
by 4.9 m/s² : 55 m / 4.9 m/s² = (time)²

   (time)² = (55/4.9) sec²

Square-root
each side: time = √(55/4.9 sec²)

   =    3.35 sec .

5 0

3 years ago

If a wire lies withina magnetic field what must be true for the magnetic field to produce an electric current in the wire

BigorU [14]

Answer:

The magnetic field through the wire must be changing

Explanation:

According to Faraday's law, the induced emf, ε in a metallic conductor is directly proportional to the rate of change of magnetic flux,Φ through it. This is stated mathematically as ε = dΦ/dt.

Now for the wire, the magnetic flux through it is given by Φ = ABcosθ where A = cross-sectional area of wire, B = magnetic field and θ = angle between A and B.

So, dΦ/dt = dABcosθ/dt

Since A and B are constant,

dΦ/dt = ABdcosθ/dt = -(dθ/dt)ABsinθ

Since dθ/dt implies a change in the angle between A and B, since A is constant, it implies that B must be rotating.

So, <u>for an electric current (or voltage) to be produced in the wire, the magnetic field must be rotating or changing</u>.

5 0

2 years ago

The formula is x = 1/2 at^2 and I have managed to fill in the variables as this. d = 1/2 9.81 m/s^2 1^2

Artyom0805 [142]

Right, as you mentioned in the comments, you find $d$ by plugging in the different values of $t$ .

For $t=1\,\mathrm s$ , we have

$d=\dfrac12\left(9.81\,\dfrac{\mathrm m}{\mathrm s^2}\right)(1\,\mathrm s)^2$

$d=\left(4.905\,\dfrac{\mathrm m}{\mathrm s^2}\right)\left(1\,\mathrm s^2\right)$

$d=4.905\,\mathrm m$

Similarly, for $t=2\,\mathrm s$ , you get

$d=\dfrac12\left(9.81\,\dfrac{\mathrm m}{\mathrm s^2}\right)\left(2\,\mathrm s\right)$

$d=\left(4.905\,\dfrac{\mathrm m}{\mathrm s^2}\right)\left(4\,\mathrm s^2\right)$

$d=19.62\,\mathrm m$

8 0

3 years ago