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Viktor [21]
3 years ago
14

A train slows down from 34 m/s to 4 m/s in 60 seconds. what is it's acceleration?

Physics
1 answer:
OverLord2011 [107]3 years ago
3 0
Acceleration = change in velocity / time

change in velocity = final velocity - initial velocity

because the object is slowing down, the acceleration will be negative.

acceleration = (4-34) / 60
acceleration = -30 / 60
acceleration = -0.5 m/s^2

answer : the train is accelerating at -0.5 m/s^2
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Identify which one is chemical change, chemical property,physical change and physical property
Ulleksa [173]

Answer:

Heat conductivity: Physical property

Silver tarnishing: chemical change

Sublimation: physical change

Magnetizing steel: physical property

Length of a metal object: physical property

Shortening melting: physical property

exploding dynamite: chemical change

combustible: chemical property

water freezing: physical change

Acid resistance: chemical property

brittleness: physical property

milk souring: chemical change

baking bread: chemical change

Explanation:

First you need to understand the differences between physical and chemical change; physical and chemical property.

<u>Physical properties vs chemical properties:</u>

Physical properties are properties that you can observe without changing the substance's composition. This means you can measure these properties without changing them chemically.

Chemical properties, on the other hand, are properties are not as direct. These properties are generally determined by the way the react with other substances changing their composition.

<u>Physical changes vs chemical changes:</u>

A substance that undergoes physical change does not change in chemical composition. They may look physically different in terms of size and shape, but overall, their chemical composition remains constant. The best example would be water. Water can change phases, from solid to liquid when they melt. Essentially, they look like different substances, but the change is only physical and not chemical.

Chemical change, is different by the fact that they change in chemical composition. Bonds are broken and/or made through the reaction, which changes them not only physically but chemically as well. Some of the most indicative signs of a chemical change occurring are: change in color, odor, production of gas, production of light/heat.

4 0
3 years ago
In a thermostat, what property of the bimetallic coil allows it to contract and expand? The two metals absorb different amounts
madam [21]
Hello!

In a thermostat, the property of the bimetallic coil that allows it to contract and expand is that The two metals absorb different amounts of thermal energy. 

This bimetallic coil is used to transform thermal energy into mechanical movement. Two metals with different thermal expansivity are joined together parallelly and the changes of temperature cause bending in different directions depending on if the temperature is rising or descending. 

The differences in the thermal energy absorption of the two metals are the basis for the mechanism of this device. 
3 0
3 years ago
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A child lifts a 5.0-newton toy to a height of 0.50 meters. How much work is done on the toy?
natali 33 [55]
Work done=mgh
W=force*height
W=5N*0.50mts
W=2.5joule
6 0
4 years ago
Read 2 more answers
Astronomersestimatethata2.0-km-diameterasteroidcollides with the Earth once every million years. The collision could pose a thre
tangare [24]

Answer:

a) 1.6*10^21 Joules.

b) 40,000

Explanation:

part a )

maximum destructive energy that can be released is the case when all the kinetic energy of the asteroid is consumed.

therefore E = 1/2 m v^2

m= density * volume

= 3100* (4/3* pi * 1000^3 ) = 12978666666666.67 kg

given v = 16000m/s

therefore

E= 1/2 * 12978666666666.67 * 16000 * 16000

= 1.6 x 10^21 Joules!

part B)

each bomb is capable of 4 x 10^16 joules

therefore no of bombs that are needed to produce the required energy are

1.6 x 10^21 / 4 x 10^16 = 40,000

that is 40,000 such nuclear bombs are required!

7 0
3 years ago
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An electric heater used to boil small amounts of water consists of a 15-Ω coil that is immersed directly in the water. It operat
Allisa [31]

Answer:

t = 1120 seconds

Explanation:

Law of Conservation of Energy: It states that energy can neither be created or destroyed but it can be transformed from one form to another

The heater converts electric energy to heat energy.

According to the law of conservation of Energy,

Heat supplied by the heater = heat gained by the water.

Heat supplied by the heater = (V²/R)t, Where V = voltage, R = Resistance, t = Time.

Heat gained by the water = cm(θ₂ -θ₁)

Where c = specific heat capacity of water, m = mass of water, θ₂= final temperature of water, θ₁= initial temperature of water.

∴ (V²/R)t =  cm(θ₂ -θ₁)

Making  t the subject of the equation,

t =  cm(θ₂ -θ₁) ×R/V²

Where c= 4200 Jkg/K, m=0.80 kg, R = 15 Ω, V = 60 V, θ₁= 20°C, θ₂ = the normal boiling point of water = 100°C

∴ t = (4200×0.8)(100 -20)×15/60²

t = (3360×80×15)/3600

t = 4032000/3600 = 1120 seconds

∴  The time required by the heater to raise the temperature of water to normal boiling point is 1120 seconds.

3 0
3 years ago
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