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vfiekz [6]
3 years ago
12

The radius of a conducting wire is doubled .What will be the ratio of its new specific resistance to the old one?

Physics
1 answer:
sladkih [1.3K]3 years ago
7 0
The equation for the resistance R is: R=ρ*(l/A), where, ρ is electrical resistivity, l is the length of the conductor, and A is the surface area.

The initial surface area is:

A=r²π, then when we double the radius we get:
 
A₁=(2*r)²π=4*r²π=4*A

Initial resistance is: R=ρ*(l/A).

When we double the radius, resistance is: R₁=ρ*{ l / (4*A) }

The ratio of the new resistance to the old one:

R₁/R=[ρ*(l/A)] / [ ρ* { l / (4*A) } ] = ρ, l and A cancel out and we get:

R₁/R=(1/1)/(1/4)=4/1 
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She must be launched with minimum speed of <u>57.67 m/s</u> to clear the 520 m gap.

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The minimum speed to cross the gap is the initial speed of the projectile and can be determined using the formula for range of projectile.

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A 20 cm tall object is placed in front of a concave mirror with a radius of 31 cm. The distance of the object to the mirror is 9
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Answer:

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Given that,

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We need to find the focal length of the mirror. The relation between the focal length and the radius of curvature of the mirror is as follows :

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f = -15.5 cm

So, the focal length of the concave mirror is -15.5 cm. Hence, this is the required solution.

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