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Ierofanga [76]
3 years ago
10

Calculate the energy needed to heat 4 kg of water from 25°C to 45°C.

Physics
2 answers:
inna [77]3 years ago
8 0
(1 cal/g °C) x (4000 g) x (45 - 25)°C = 80000 cal = 80 kcal. So the answer is 80 kcal .
melisa1 [442]3 years ago
4 0

Answer:

80 Kcal

Explanation:

Specific heat is the energy required to raise the temperature of a unit mass of a substance by one degree. Its units are kJ/kg·K or kJ/kg·°C in the SI system.

There are two types of specific heat: 1) when the process is at constant volume. 2) When it's at constant pressure. In the case of liquids, the value is the same for the two cases. The specific heat of water is equal to 4.18kJ/kg·°C (in that range of temperatures)

The formula which relates energy needed, specific heat, change in temperature, and mass of the substance is the following:

ΔU=m·c·(T2-T1)

T2: final temperature of the substance

T1: initial temperature of the substance

c: specific heat of the substance

m: the mass of the substance

ΔU: energy required to raise the temperature the substance from T1 to T2

Plugging the given values values on the equation:

ΔU=4kg·(4.18kJ/kg·°C)·(45°C-25°C)

ΔU=334.4kJ

Now, it only rests to convert from kJ to cal:

1kJ=0.2390kcal

So:

334.4kJ=334.4*0.2390kcal=79.9kcal≈80kcal

So the energy needed to heat 4 kg of water from 25°C to 45°C is 80kcal

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Heat flows into a gas in a piston and work is performed on the gas by its surroundings. The amount of work done is equal to the
inna [77]

Answer:

The Internal energy of the gas did not change

Explanation:

In this situation the Internal energy of the gas did not change and this is because according the the first law of thermodynamics

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since Q = W.  the value of ΔU  will be = zero   i.e. No change

4 0
3 years ago
12. A frain moves from rest to a speed of 25 m/s in 30.0 seconds. What is its acceleration?
ziro4ka [17]
  • initial velocity=u=0m/s
  • Final velocity=v=25m/s
  • Time=t=30s

\\ \tt\longmapsto Acceleration=\dfrac{v-u}{t}

\\ \tt\longmapsto Acceleration=\dfrac{25-0}{30}

\\ \tt\longmapsto Acceleration=\dfrac{25}{30}

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6 0
3 years ago
uppose two train cars are moving toward one another, the first with a mass of 150,000 kg and a velocity of 0.300 m/s; the second
kondaur [170]

The value was determined to be 0.122 m/s. The velocity of a body or object determines its direction of motion. Speed is a scalar quantity in its most fundamental form.

Velocity is essentially a vector quantity. It is the rate of change in distance. The initial speed of the first train, which has a mass of 150,000 kg, is 0.3 m/s. The second train has an initial speed of -0.120 m/s and a mass of 110,000 kg.

Let v represent the post-collision speed of the connected mass.

Utilize the idea of momentum.

The speed of the trains is constant both before and after a collision.

150.000 + 110.000v 45.000 - 13200 = 260.000 v 31800 = 260.000 v v = 0.122 m/s 150000 x 0.3 - 110000 x 0.120

After colliding, they move at a speed of 0.122 m/s towards the direction of the right.

Learn more about velocity here-

brainly.com/question/18084516

#SPJ4

7 0
1 year ago
Try this out. Use a calculator!
Maslowich
Just subsitute and easy
v=55m/s
m=100kg
KE=(0.5)(100kg)(55m/s)^2
KE=(50kg)(3025 m^2/s^2)
KE=151250 J
2nd option
6 0
3 years ago
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