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3 years ago

Which of the following is the best definition of a closed system?

Physics

1 answer:

lisov135 [29]3 years ago

4 0

The answer is either

b A system in which Newton's Laws are valid

c A system in which there are no external forces.

Explanation:

not a, and not d

There are energy changes in a closed system.

A closed system obeys the conservation laws in its physical description.

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A copper wire has a radius of 3.5 mm. When forces of a certain equal magnitude but opposite directions are applied to the ends o

denpristay [2]

Answer:

The tensile stress on the wire is 550 MPa.

Explanation:

Given;

Radius of copper wire, R = 3.5 mm

extension of the copper wire, e = 5.0×10⁻³ L

L is the original length of the copper wire,

Young's modulus for copper, Y = 11×10¹⁰Pa.

Young's modulus, Y is given as the ratio of tensile stress to tensile strain, measured in the same unit as Young's modulus.

$Y =\frac{Tensile \ stress}{Tensile \ strain} \\\\Tensile \ stress = Y*Tensile \ strain\\\\But, Tensile \ strain = \frac{extension}{original \ Length} = \frac{5.0*10^{-3} L}{L} = 5.0*10^{-3}\\\\Tensile \ stress = 11*10^{10} *5.0*10^{-3} \ = 550*10^6 \ Pa$

Therefore, the tensile stress on the wire is 550 MPa.

8 0

3 years ago

The magnitude of the magnetic field B a distance r from a long straight wire is B = μ 0 I 2 π r where μ 0 is the permeability co

PSYCHO15rus [73]

Answer:

The magnetic field is lowest for largest distance and highest when distance is least.

Explanation:

The magnitude of magnetic field strength at a distance 'r' from a long straight wire carrying current 'I' is given as:

$B=\frac{\mu_0 I}{2\pi r}\\Where,\mu_0\to permeability\ constant\ of\ free\ space$

Now, as per question, the distance 'r' is varied while keeping the current constant in the wire.

As seen from the above formula, the magnitude of magnetic field strength for a constant current varies inversely with the distance 'r'. This means that, as the value of 'r' increases, the magnitude of magnetic field strength decreases and vice-versa.

Therefore, the magnitude of magnetic field strength is maximum when the distance 'r' is least and the magnetic field is minimum for the largest distance.

Example:

If $B_1, B_2,\ and\ B_3$ are the magnitudes of magnetic field strengths for distances $r_1,r_2, \ and\ r_3$ respectively such that $r_1$ . Now, as per the explanation above, the order of magnitudes of magnetic field strength is:

$B_1>B_2>B_3$

6 0

4 years ago

A bicycle and a car start their journey at the same time the cyclist reaches it's top speed of 10mls in 15 the car reaches a spe

Y_Kistochka [10]

Complete question is;

A bicycle and a car start their journey at the same time the cyclist reaches it's top speed of 10m/s in 15 s, the car reaches a speed of 15 m/s in 55 s. which has the greater acceleration the car or the bicycle.

Answer:

The bicycle has the greater acceleration.

Explanation:

Cyclist reaches a top speed of 10m/s in 15 s.

Formula for acceleration here is;

a = v/t

a = 10/15

a = 0.67 m/s²

Car reaches a speed of 15 m/s in 55 s.

Thus;

a = 15/55

a = 0.27 m/s²

From the 2 acceleration values gotten, we can say that;

The bicycle has the greater acceleration.

6 0

3 years ago

A runner taking part in the 200 m dash must run around the end of a track that has a circular arc with a radius of curvature of

nlexa [21]

Answer:

$a_c=1.44\ m/s^2$

Explanation:

<u>Centripetal Acceleration</u>

It's the acceleration that an object has when traveling on a circular path to take into consideration the constant change of velocity it must have in order to keep going in the circular path.

Being v the tangent speed, and r the radius of curvature of the circle, then the centripetal acceleration is given by

$\displaystyle a_c=\frac{v^2}{r}$