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77julia77 [94]
3 years ago
14

Wнιcн deмonѕтraтeѕ condυcтιon

Physics
1 answer:
jekas [21]3 years ago
3 0

C.) cool feet walking across a hot pavement.



The reason because the other ones deals with radiation. Only C.) is the right answer because the feet is touching the hot pavement which is conduction. 
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Find the angle formed by two forces of 7N and 15N respectively if its result is worth 20N
nadezda [96]
First, you need to make certain assumptions before solving this question. Why? Because there are no information given about the direction of these forces. In such questions as above, ALWAYS make the following assumptions:

1) Take first force, say F_{1}, and assume that it is pointing towards the x-direction.

Let us take the 7N force! By keeping the above assumption in our minds, the force vector would be like:
F_{1} = 7i, where i = Unit vector in the x-direction.

2) Take the second force, say F_{2}, and assume that it is making an angle \alpha with the first force F_{1}.

Let us take the 15N force! By keeping the above assumption in our minds, the forces vector would be like:

F_{2} = (15*cos \alpha)i + (15*sin \alpha )j

Now from simple vector addition, we know that,
F_{R} = F_{1} + F_{2} --- (A)

Where F_{R} = Resultant vector.
NOTE: In equation (A), all forces are in vector notation. Assume that there is an arrow head on top of them.

Let us find F_{1}+F_{2} first!
F_{1}+F_{2} =  7i+(15*cos \alpha)i + (15*sin \alpha )j

=> F_{1}+F_{2} =  (7+15*cos \alpha)i + (15*sin \alpha )j

Now the magnitude of F_{1}+F_{2} is,
| F_{1}+F_{2}| = \sqrt{ (7+ 15*cos \alpha)^{2} +  (15*sin \alpha )^{2}}

=> | F_{1}+F_{2}| = \sqrt{ 49 + 225*(cos \alpha)^{2} + 210*(cos \alpha)+ 255*(sin \alpha )^{2}}

Since (sin \alpha)^{2} + (cos \alpha)^{2} = 1, therefore,

=> | F_{1}+F_{2}| = \sqrt{ 49 + 225 + 210*(cos \alpha)}

Since  | F_{1}+F_{2}| = |F_{R}|, and the magnitude of the resultant force is 20N, therefore,

 |F_{R}| = | F_{1}+F_{2}|
20 = \sqrt{ 49 + 225 + 210*(cos \alpha)}

Take square on both sides,
400 = 49 + 225 + 210*(cos \alpha)
(cos \alpha) =  \frac{3}{5}

\alpha = 53.13^{o}

Ans: Angle formed by the two forces, 7N and 15N, is: 53.13°

-israr

4 0
2 years ago
If an amount of heat Q is needed to increase the temperature of a solid metal sphere of diameter D from 4°C to 7°C, the amount o
Hitman42 [59]

Answer:

Q = c M ΔT      where c is the heat capacity and M the mass present

Q2 / Q1 = M2 / M1    since the other factors are the same

M = ρ V     where ρ is the density

M = ρ Π (d / 2)^2           where d is the diameter of the sphere

M2 / M1 = (2 D/2)^2 / (D/2)^2 = 4

It will take 4Q heat to heat the second sphere

7 0
2 years ago
Current explanation of where electrons might be found in the atom
Paul [167]

Answer:

Outer Shell

Explanation:

an electron of an atom, located in the outermost shell (valence shell) of the atom, that can be transferred to or shared with another atom. An electron in one of the outer shells of an atom that can participate in forming chemical bonds with other atoms. read more

8 0
3 years ago
Desperate for help! please!!!!!!!!
lys-0071 [83]

0.4029 \mathrm{m} / \mathrm{s}^{2} is the acceleration of the box.

<u>Explanation:</u>

Given data:

Mass of the box = 3.74 kg

Flat friction-less ground is pulled forward by a 4.20 N force at a 50.0 degree angle and pulled back by a 2.25 N force at a 122 degree angle.

First, we need to find the net horizontal force acting on the box. With the given data, the equation can be formed as below.  Net horizontal force acting on the box (F) is given by

F=\left(4.20 \times \cos 50^{\circ}\right)+\left(2.25 \times \cos 122^{\circ}\right)

F=(4.20 \times 0.64278)+(2.25 \times-0.5299)

F = 2.699676 – 1.192275 = 1.507 N

Next, find acceleration of the box using Newton's second law of motion. This states that the link between mass (m) of an objects and the force (F) required to accelerate it. The equation can be given as

F=m \times acceleration\ (a)

\text {acceleration }(a)=\frac{F}{m}=\frac{1.507}{3.74}=0.4029 \mathrm{m} / \mathrm{s}^{2}

8 0
3 years ago
Please help will give brainliest
andreyandreev [35.5K]
The answer is A.
It will decay to give you Thorium and Helium.

Please give me Brainliest.
4 0
3 years ago
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