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Kamila [148]
3 years ago
13

A resistor is made by winding a very long thin metal wire, insulated so adjacent coils do not touch. At room temperature, the re

sistance is 100 ohms.
If the resistor is then cooled to 77 K, the resistance:

A. changes only slightly, if at all.
B. increases significantly (more than a factor of two).
C. decreases significantly (more than a factor of 1/2).
Physics
1 answer:
Vladimir79 [104]3 years ago
3 0

Answer:

Option A

Explanation:

The correct answer is  Option A.

At room temperature, the resistance is equal to 100 ohms.

When the temperature is reduced to 77 K from room temperature, change in the resistance is very less.

The temperature coefficient of the resistivity of most of the metal is small for the metals which are approximately equal  0.01 /K.

hence, Change is only slightly.

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3 years ago
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The gravitational force between two objects is 2400 N. What will be the gravitational force between the objects if the mass of o
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Answer:

4800N

Explanation:

Lets assume,

Mass of first object = m₁

Mass of second object = m₂

Distance between the two objects = r

Thus the force between the two objects will be

F = \frac{G\times m_{1}\times m_{2}}{r^{2}}

where, G = Universal gravitational constant

Given, F = 2400N

New mass of second object = 2m₂

Now, the force will be

F_{2} = \frac{G\times m_{1}\times 2m_{2}}{r^{2}}

F_{2}= 2\frac{G\times m_{1}\times m_{2}}{r^{2}}

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1-A car moves toward east 12km is represented as A and it turns towards south 16km is represented as B. What is the resultant ve
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1. A-20 km south east

The car's displacement consists of two components into two different directions. Using a system of coordinates in which x represents the east direction and y represents the south direction, the two displacements are:

d_x = 12 km east

d_y = 16 km south

Since the two components are orthogonal to each other, we can find the resultant displacement by using Pythagorean's theorem:

d=\sqrt{d_x^2+d_y^2}=\sqrt{(12 km)^2+(16 km)^2}=\sqrt{400}=20 km

and the direction is between the two original directions, so south-east.

2. D. 10 m/s

First of all, we need to calculate the total time the stone took to hit the ground. Since the vertical distance covered is S = 78.4 m, and since the motion is an accelerated motion with constant acceleration g=9.8 m/s^2, we have

S=\frac{1}{2}gt^2

From which we find the total time of the fall, t:

t=\sqrt{\frac{2S}{g}}=\sqrt{\frac{2(78.4 m)}{9.8 m/s^2}}=4 s

Now we can consider the horizontal motion of the stone: we know that the stone travels for d = 40 m in a time of t = 4 s, therefore the horizontal velocity of the stone is

v=\frac{d}{t}=\frac{40 m}{4 s}=10 m/s

3. B=32.32 m

As in the previous problem, we have to calculate the total time it takes for the stone to reach the river first. Since the vertical distance covered is S = 20 m, we have

t=\sqrt{\frac{2S}{g}}=\sqrt{\frac{2(20 m)}{9.8 m/s^2}}=2.0 s

And since the stone is traveling horizontally at v = 16 m/s, the horizontal distance covered is

d=vt=(16 m/s)(2 s)=32 m

So, the closest answer is B.

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