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3 years ago

What 2 kinds of substances does convection occur ?

Physics

1 answer:

ch4aika [34]3 years ago

4 0

Liquids and Gases

Explanation:

Convection is a form of heat transfer that is predominant in liquids and gaseous substances. This form of heat transfer is driven by density differences between gases and liquids.

Convection involves the actual movement of the particles of a medium.
Boiling of food is clinical example of convection in liquids. Hot part of the food in contact with the heat source becomes less dense and more buoyant. They rise to the top of the medium and are replace by the denser and colder part of the food.
Land and sea breeze is an example of convection in gases. The land warms the air around it during the day. It is hotter and less dense. The air mass moves to replace the ones on the sea where the air is relatively cold due to high specific heat capacity of water.
The reverse process occurs at night.

Learn more:

Heat transfer from the sun brainly.com/question/1140127

#learnwithBrainly

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A ball is thrown from the top of one building toward a tall building 50 m away. The initial velocity of the ball is 20 m/s at 40

Vinvika [58]

Answer:

Ball hit the tall building 50 m away below 10.20 m its original level

Explanation:

Horizontal speed = 20 cos40 = 15.32 m/s

Horizontal displacement = 50 m

Horizontal acceleration = 0 m/s²

Substituting in s = ut + 0.5at²

50 = 15.32 t + 0.5 x 0 x t²

t = 3.26 s

Now we need to find how much vertical distance ball travels in 3.26 s.

Initial vertical speed = 20 sin40 = 12.86 m/s

Time = 3.26 s

Vertical acceleration = -9.81 m/s²

Substituting in s = ut + 0.5at²

s = 12.86 x 3.26 + 0.5 x -9.81 x 3.26²

s = -10.20 m

So ball hit the tall building 50 m away below 10.20 m its original level

5 0

2 years ago

You have been hired to design a spring-launched roller coaster that will carry two passengers per car. The car goes up a 12-m-hi

Vlada [557]

Answer:

Vmax=11.53 m/s

Explanation:

from conservation of energy

$E_A} =E_{B}$

Spring potential energy =potential energy due to elevation

0.5*k*x²= mg $(h_{B}-h_{A} )$ =mgh

0.5*k*2.3²= 430*9.81*6

k=9568.92 N/m

For safety reason

k"=1.13 *k= 1.13*9568.92

k"=10812.88 N/m

agsin from conservation of energy

$E_A} =E_{C}$

spring potential energy=change in kinetic energy

0.5*k"*x²=0.5*m* $V_{max}^{2}$

10812.88 *2.3²=430* $V_{max}^{2}$

$V_{max}$ =11.53 m/s

5 0

3 years ago

What is the minimal mass of helium (density 0.18 kg/m3) needed to lift a balloon carrying two people in a basket, if the total m

Sergio039 [100]

Answer:
M[min] = M[basket+people+ balloon, not gas] * Î”R/R[b]
Î”R is the difference in density between the gas inside and surrounding the balloon.
R[b] is the density of gas inside the baloon.
====================================
Let V be the volume of helium required.
Upthrust on helium = Weight of the volume of air displaced = Density of air * g * Volume of helium = 1.225 * g * V
U = 1.225gV newtons
----
Weight of Helium = Volume of Helium * Density of Helium * g
W[h] = 0.18gV N
Net Upward force produced by helium, F = Upthrust - Weight = (1.225-0.18) gV = 1.045gV N  -----

Weight of 260kg = 2549.7 N
Then to lift the whole thing, F > 2549.7
So minimal F would be 2549.7
----
1.045gV = 2549.7
V = 248.8 m^3
Mass of helium required = V * Density of Helium = 248.8 * 0.18 = 44.8kg (3sf)
=====
Let the density of the surroundings be R
Then U-W = (1-0.9)RgV = 0.1RgV
So 0.1RgV = 2549.7 N
V = 2549.7 / 0.1Rg
Assuming that R is again 1.255, V = 2071.7 m^3
Then mass of hot air required = 230.2 * 0.9R = 2340 kg
Notice from this that M = 2549.7/0.9Rg * 0.1R so
M[min] = Weight of basket * (difference in density between balloon's gas and surroundings / density of gas in balloon)
M[min] = M[basket] * Î”R/R[b]

3 0

3 years ago

Sasha lifts a couch 8.2 meters from the ground floor of her house to the attic. If the couch has a mass of 120 kg, what is the g

gavmur [86]

As we know that gravitational potential energy is given by

$U = mgH$

here we have

m = mass = 120 kg

$g = 9.81 m/s^2$

h = height = 8.2 m

now from above formula

$U = 120kg (9.81 m/s^2) (8.2 m)$

$U = 9653.04 J$

so above is the gravitational potential energy of the couch

4 0

3 years ago

Read 2 more answers

A baseball with a mass of 151 g is thrown horizontally with a speed of 39.5 m/s (88 mi/h) at a bat. The ball is in contact with

Oduvanchick [21]

Answer:

the average force exerted on the ball by the bat is 11,613.27 N

Explanation:

Given;

mass of the baseball, m = 151 g = 0.151 kg

initial velocity of the baseball, u = 39.5 m/s

final velocity of the baseball, v = 45.1 m/s

time of action, t = 1.10 ms = 1.10 x 10⁻³ s

The average force exerted on the ball by the bat is calculate as;

$F = ma = \frac{m(v-u)}{t} \\\\F = \frac{0.151(45.1-(-39.5))}{1.10\times 10^{-3}} \\\\F = \frac{0.151(45.1\ +\ 39.5)}{1.10\times 10^{-3}} \\\\F = 11,613.27 \ N$

Therefore, the average force exerted on the ball by the bat is 11,613.27 N

7 0

2 years ago