PHYSICS
HIGH SCHOOL

Answer: Density is a value for mass, such as kg, divided by a value for volume, such as m^3. Density is a physical property of a substance that represents the mass of that substance per unit volume. The mass of the salty water is calculated as follows:

Mass = 1.166 g/mL ( 2000 mL ) = 2332 g of salty water

Mass = 1.166 g/mL ( 2000 mL ) = 2332 g of salty water

COLLEGE

An aluminum wire with a diameter of 0.125 mm has a uniform electric field of 0.305 V/m imposed along its entire length. The temperature of the wire is 45.0° C. Assume one free electron per atom. (a) What is the current density in the wire?

(b) What is the total current in the wire?

Answer:

(a) Current density is 1.05 x 10⁷ A/m²

(b) Total current in the wire is 0.129 A.

Explanation:

As in the problem, the resistivity of aluminium is not mention. SO, we consider the case in which resistivity of aluminium is 2.65 x 10⁻⁸ ohm m at 20⁰ C.

The resistivity of the material depend upon the temperature by the equation:

р = р₀ [1 + α(T - T₀) ]

Here р is resistivity at temperature T, р₀ is resistivity at temperature T₀ and

α is constant.

Put 2.65 x 10⁻⁸ ohm m for р₀, 45° C for T, 20° C for T₀ and 3.9 x 10⁻³ /°C for α in the above equation.

р =

р = 2.90 x 10⁻⁸ ohm m

(a) The relation between electric field and current density is:

J = E/р

Substitute 0.305 V/m for E and 2.90 x 10⁻⁸ ohm m for р in the above equation.

J =

J = 1.05 x 10⁷ A/m²

(b) The relation between current and current density is :

I = J x A

Here A is the area.

Area of wire, A = π (d/2)²

Here d is the diameter of the wire.

So, I = J x π (d/2)²

Substitute 1.05 x 10⁷ A/m² for J and 0.125 x 10⁻³ m for d in the above equation.

I =

I = 0.129 A

HIGH SCHOOL

How are important properties of Mercury, Venus, and Mars different from important properties of Earth?

Hi there,

There is one thing that is the most difference about other planets. Earth is a perfect condition for humans, animals, and other living things. Venus and Mars are not quite good for that. Venus has a very HOT surface, which makes it nearly impossible to be on. Mars on the other hand is very COLD, colder than earth because it is farther from the sun.

There is one thing that is the most difference about other planets. Earth is a perfect condition for humans, animals, and other living things. Venus and Mars are not quite good for that. Venus has a very HOT surface, which makes it nearly impossible to be on. Mars on the other hand is very COLD, colder than earth because it is farther from the sun.

COLLEGE

A ball is whirled on the end of a string in a horizontal circle of radius R at const v. By which one of the following means can the centripetal acceleration of the b increased by a factor of two? 13. Keep the radius fixed and increase the period by a factor of two. Keep the radius fixed and decrease the period by a factor of two. Keep the speed fixed and increase the radius by a factor of two. Keep the speed fixed and decrease the radius by a factor of two. A) B) C) D)

Answer:

D

Explanation:

Centripetal acceleration is the square of velocity divided by radius:

a = v² / r

Velocity is equal to angular velocity times radius, so this can also be written as:

a = ω² r

And angular velocity is 2π divided by the period, so:

a = (2π / T)² r

We can use these two equations to determine which scenario results in double the centripetal acceleration.

A) Keep the radius fixed and increase the period by a factor of two.

(2π / 2T)² r

1/4 (2π / T)² r

1/4 a

B) Keep the radius fixed and decrease the period by a factor of two.

(2π / ½T)² r

4 (2π / T)² r

4a

C) Keep the speed fixed and increase the radius by a factor of two.

v² / 2r

1/2 a

D) Keep the speed fixed and decrease the radius by a factor of two.

v² / ½r

2a

Only D doubles the centripetal acceleration.

HIGH SCHOOL

The force of an apple hitting the ground depends on

I believe it depends on gravity and KE(kinetic energy0