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3 years ago

Joaquin mows the lawn at his grandmother’s home during the summer months. Joaquin measured the

1 answer:

7 0

Velocity is define as how fast an object is moving, and in what direction, it is a vector quantity, meaning velocity has both magnitude and direction. Anything goes to the left is negative, and anything goes to the right is positive.

a. Direction from east to west, given distance 11.5 meters, and time of 7.10 s

V = displacement/time V = -11.5/7.10 S V = -1.62 m/s (going left)

b. Joaquin reaches his original position. Displacement is now zero.

Velocity of the lawnmower is equal to "zero" but if we calculate for the average speed of the lawn, you just have to add the distance covered and the time it take to go back at the original position or point of origin

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A wall in a house contains a single window. The window consists of a single pane of glass whose area is 0.15 m2 and whose thickn

KengaRu [80]

Answer:

88 %

Explanation:

The rate of heat loss by a conducting material of thermal conductivity K, cross-sectional area,A and thickness d with a temperature gradient ΔT is given by

P = KAΔT/d

The total heat lost by the styrofoam wall is P₁ = K₁A₁ΔT₁/d₁ where K₁ =thermal conductivity of styrofoam wall 0.033 W/m-K, A₁ = area of styrofoam wall = 17 m², ΔT₁ = temperature gradient between inside and outside of the wall and d₁ = thickness of styrofoam wall = 0.20 m

The total heat lost by the glass window is P₂ = K₂A₂ΔT₂/d₂ where K₂ =thermal conductivity of glass window pane wall 0.96 W/m-K, A₂ = area of glass window pane = 0.15 m², ΔT₂ = temperature gradient between inside and outside of the window and d₂ = thickness of glass window pane = 7 mm = 0.007 m

The total heat lost is P = P₁ + P₂ = K₁A₁ΔT₁/d₁ + K₂A₂ΔT₂/d₂

Now, since the temperatures of both inside and outside of both window and wall are the same, ΔT₁ = ΔT₂ = ΔT

So, P = K₁A₁ΔT/d₁ + K₂A₂ΔT/d₂

Since P₂ = K₂A₂ΔT₂/d₂ = K₂A₂ΔT/d₂is the heat lost by the window, the fraction of the heat lost by the window from the total heat lost is

P₂/P = K₂A₂ΔT/d₂ ÷ (K₁A₁ΔT/d₁ + K₂A₂ΔT/d₂)

= 1/(K₁A₁ΔT/d₁÷K₂A₂ΔT/d₂ + 1)

= 1/(K₁A₁d₂÷K₂A₂d₁ + 1)

= 1/[(0.033 W/m-K × 17 m² × 0.007 m ÷ 0.96 W/m-K × 0.15 m² × 0.20 m) + 1]

= 1/(0.003927/0.0288 + 1)

= 1/(0.1364 + 1)

= 1/1.1364

= 0.88.

The percentage is thus P₂/P × 100 % = 0.88 × 100 % = 88 %

The percentage of heat lost by window of the total heat is 88 %

6 0

3 years ago

The surface temperature of our sun is about 5800 K, and the peak of its intensity curve is in the middle of the visible spectrum

amm1812

Explanation:

i expected to use Stefan's law of heat exchange but the value you gave aren't conclusive.

I should say that the temperature of the star should be close to that of the sun because of the similarity in the intensity curves

3 0

2 years ago

Uest<br>1. State Newton's law of cooling.

garik1379 [7]

Answer:

Newton's law of cooling states that the rate of heat loss of a body is directly proportional to the difference in the temperatures between the body and its surroundings. The law is frequently qualified to include the condition that the temperature difference is small and the nature of heat transfer mechanism remains the same. As such, it is equivalent to a statement that the heat transfer coefficient, which mediates between heat losses and temperature differences, is a constant. This condition is generally met in heat conduction (where it is guaranteed by Fourier's law) as the thermal conductivity of most materials is only weakly dependent on temperature. In convective heat transfer, Newton's Law is followed for forced air or pumped fluid cooling, where the properties of the fluid do not vary strongly with temperature, but it is only approximately true for buoyancy-driven convection, where the velocity of the flow increases with temperature difference. Finally, in the case of heat transfer by thermal radiation, Newton's law of cooling holds only for very small temperature differences.

When stated in terms of temperature differences, Newton's law (with several further simplifying assumptions, such as a low Biot number and a temperature-independent heat capacity) results in a simple differential equation expressing temperature-difference as a function of time. The solution to that equation describes an exponential decrease of temperature-difference over time. This characteristic decay of the temperature-difference is also associated with Newton's law of cooling

6 0

3 years ago

What three things can happen to water when it falls on earth's surface

777dan777 [17]

It can be stored on the land surface as ice and snow...it can seep into the earth and be stored as surface water...it can flow in the surface of lands.

3 0

3 years ago

Because of barriers and obstructions, you can see only a tiny fraction of a standing wave on a string. You do not know, for inst

chubhunter [2.5K]

Answer:

(1) Sure, the frequency is 1000 Hz.

Explanation:

Frequency = wave speed ÷ wave distance

wave speed = 100 m/s

wave distance = 10 cm = 10/100 = 0.1 m

Frequency = 100 ÷ 0.1 = 1000 Hz

4 0

3 years ago

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