Answer:
7800 J
Explanation:
Heat needed = mass of copper x specific heat of copper x change in temperature
Change in temperature = 30ºC - 20ºC = 10ºC
Specific heat of copper = 390 J/kgºC
Mass of copper = 2 Kg
Substituting the given values in above equation, we get –
Heat needed = 2 Kg x 390 J/kgºC x 10ºC
= 7800 J
OK. So you're pushing on the small box, and on the other side of it, the small
box is pushing on the big box. So you're actually pushing both of them.
-- The total mass that you're pushing is (5.2 + 7.4) = 12.6 kg.
-- You're pushing it with 5.0N of force.
-- Acceleration of the whole thing = (force)/(mass) = 5/12.6 = <em>0.397 m/s²</em> (rounded)
-- Both boxes accelerate at the same rate. So the box farther away from you ...
the big one, with 7.4 kg of mass, accelerates at the same rate.
The force on it to make it accelerate is (mass) x (acceleration) =
(7.4 kg) x (5/12.6 m/s²) = <em>2.936 N.</em>
The only force on the big box comes from the small box, pushing it from behind.
So that same <em>2.936N</em> must be the contact force between the boxes.
A wire has a diameter of 2. 0 mm and a length of 32 m and is found to have a resistance of 1. 8 ω having a resistivity of the wire
Resistivity, which is frequently denoted by the letter rho, is mathematically equal to the resistance R of a specimen, such as a wire, multiplied by its cross-sectional area A, and divided by its length l; it is represented by the symbol RA/l. The ohm is the unit of resistance.
A conductor's resistance (R) is inversely proportional to its length (L), with R L. We now know the variables that affect resistivity. Ohm's law and resistors have also been covered in relation to parallel formulae.
The resistance provided by the substance per unit length for unit cross-section is referred to as a conductor's resistivity. Temperature and pressure affect the material's resistivity, which is a property. When compared to the resistivity of insulators, conductors have a low resistivity.
To learn more about resistivity please visit -
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Power in a wire where current is flowing can be calculated from the product of the square of the current and the resistance. Resistance is equal to the product of resistivity and length divided by the area of the wire. We do as follows:
Resistance = 2.44 × 10-8 ( 0.11) / (π)(0.0009)^2 = 1.055x10^-3 <span>Ω
P = I^2R = .170^2 (</span>1.055x10^-3 ) = 3.048x10^-5 W
Answer:
Explanation:
See the attached figure . See the forces acting on man pulling up the box .
Man is stationary so net force acting on man is zero .
T + R = Wman
R is the reaction force of the ground of second floor .
R = Wman - T
