PHYSICS MIDDLE SCHOOL

What is the final temperature when a 3.0 kg gold bar at 99 0C is dropped into 0.22 kg of water at 25oC?

Answers

Answer 1

Answer:

Answer:

46.9 C

Explanation:

The heat released by the gold bar is equal to the heat absorbed by the water:

$m_g C_g (T_g-T_f)=m_w C_w (T_f-T_w)$

where:

$m_g = 3.0 kg$ is the mass of the gold bar

$C_g=129 J/kg C$ is the specific heat of gold

$T_g=99 C$ is the initial temperature of the gold bar

$m_w = 0.22 kg$ is the mass of the water

$C_w=4186 J/kg C$ is the specific heat of water

$T_w=25 C$ is the initial temperature of the water

$T_f$ is the final temperature of both gold and water at equilibrium

We can re-arrange the formula and solve for T_f, so we find:

$m_g C_g T_g -m_g C_g T_f = m_w C_w T_f - m_w C_w T_w\nm_g C_g T_g +m_w C_w T_w= m_w C_w T_f +m_g C_g T_f \nT_f=(m_g C_g T_g +m_w C_w T_w)/(m_w C_w + m_g C_g)=\n=((3.0)(129)(99)+(0.22)(4186)(25))/((0.22)(4186)+(3.0)(129))=(38313+23023)/(921+387)=(61336)/(1308)=46.9 C$

Answer 2

Answer:

Answer:

$T_(f)=46.9C$

Explanation:

Given:

$m_(g) =3.0kg$ $m_(w) =0.22kg$

$T_(g)=99 C$ $T_(w)=25C$

$c_(p,g)=129J/kg.C$ $c_(p,w)=4186J/kg.C$

Unkown:

$T_f=?$

Formula:

$T_f=(m_g.c_(p,g).T_g+m_w.c_(p,w).T_w)/(m_w.c_(p,w)+m_g.c_(p,g))$

Step by step solution:

$T_f=((3)(129)(99)+(0.22)(4186)(25))/((0.22)(4186)+(3)(129))$

$T_f=(61336)/(1308)$

$T_f=46.9C$

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What effect would the temperature have on the time kept by a pendulum clock if the pendulum rod increase in length with an increase in temperature

Answers

As we know the time period of pendulum is given by the equation

$T = 2\pi \sqrt{(L)/(g)}$

so here

L = length of the pendulum

Now on increasing the temperature due to thermal expansion the length of the pendulum will increase and due to this the time period of the pendulum will also increase

Now due to increase in time period of the pendulum the clock will become slow and it will give incorrect time due to this increase in temperature

Thermal expansion increases the pendulum period, and the clock will lose time

Further explanation

Simple Harmonic Motion is the motion of an object (repetitive movement) through its equilibrium point where the frequency of vibrations / oscillation per second is constant

The motion that occurs in the pendulum is one example of simple harmonic motion

Terms used:

Deviation (y): the object's distance from the balance point
Amplitude (A): maximum deviation
frequency (f): number of vibrations at any time
Period (T): the amount of time in one vibration

Whereas the relationship T and f:

$\displaystyle T=(1)/(f)\n\nf=(n)/(t)$

n = number of vibrations / oscillation

t = time (s)

Formula used:

$\large{\boxed{\bold{T=2\pi \sqrt{(L)/(g) }}}\rightarrow (1)/(f)=2\pi \sqrt{(L)/(g) }$

From this formula shows that the period is proportional to the length of the pendulum rod.The longer the pendulum rod , the greater the amount of time in one vibration

If thermal expansion occurs in the pendulum clocks, the pendulum rod changes in length ,proportional to the temperature change, and increases the pendulum period, so the clock will lose time

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Suppose the initial kinetic energy and final potential energy in an experiment are both zero. What can you conclude? A. The final kinetic energy is zero. B. The initial potential energy is zero. C. The final kinetic energy is equal to the initial potential energy. D. The sum of the initial and final kinetic energies is zero.

Answers

Answer:

C. The final kinetic energy is equal to the initial potential energy.

Explanation:

Based on the Principle of energy conservation:

Sum of the Initial Energy = Sum of the Final Energy

Initial Kinetic Energy + Initial Potential Energy = Final Kinetic Energy + Final Potential Energy..........(1)

Since according to the question:

Initial Kinetic Energy = 0

Final Potential Energy = 0

The equation (1) above reduces to

Initial Potential Energy = Final Kinetic Energy

What unsusual characteristic do the cysts of brine shrimps, the resurrection fern and Tardigrades. What adaptations do they have which enable them to survive when other organisms would die?

Any help would be much appreciated.

Answers

Brine shrimps can reproduce in two ways. 1) viviparious or live reproduction and 2) oviparious or production of eggs that hatch after being expelled from the body. The eggs, coated in chorion coating, are called cysts.

Through the reproduction of cysts, the survival of brine shrimps increase even when dealing in extreme conditions. The cysts can remain in total stasis for two years in oxygen less surroundings, they can survive freezing temperature and boiling tempreture. When conditions improve and eggs are placed in salt water, they hatch within a few hours and increase the population of brine shrimps.

Resurrection ferns are called as such because they resurrect after they shrivel, though the fern does not really die. In extremely hot or conditions, these ferns can lose 75% of their water content, even losing 97% water content if suffering under extreme drought, causing them to shrivel and look like dead ferns. But, when these ferns are again exposed to water, they resurrect and becomes green and healthy. This unusual ability help these ferns to survive under extremely harmful conditions.

Tardigrades are known as nature's toughest animals. They can live in solid ice, intense radiation of space, and boiling water. They can also survive in the desert for ten years without drinking water, as well as, in the deepest part of the sea. Their survival is based on their unusual characteristic to change their form to survive without water.

In the absence of water, tardigrades can completely dry out. The absence of water in their body urges them to replace it with a sugar called trehalose. Trehalose then becomes their source of life until water becomes available to tardigrades for consumption.

A mass of gas under constant pressure occupies a volume of 0.5 m3 at a temperature of 20 degree Celsius. Using the formula for cubic expansion, what will be the volume at a temperature of 45 degree Celsius without a change in pressure?A) 0.5228938 m3
B) 0.0228938 m3
C) 0.5457875 m3
D) 0.0457875 m3

Answers

Answer: C) 0.5457875 $m^3$

Explanation: Charles' Law: This law states that volume is directly proportional to the temperature of the gas at constant pressure and number of moles.

$V\propto T$ (At constant pressure and number of moles)

$(V_1)/(T_1)=(V_2)/(T_2)$

where,

$V_1$ = initial volume of gas = $0.5m^3$

$T_1$ = initial temperature of gas = $20^oC=273.15+20=293.15K$

$V_2$ = final volume of gas = 0?

$T_2$ = final temperature of gas = $45^oC=273.15+45=318.15K$

$(0.5)/(293.15)=(V_2)/(318.15)$

$V_2=0.5457875m^3$

Thus the final volume is $0.5457875m^3$

the answer is C 0.5457875

What kind of friction exists between solid objects moving in water?static friction
sliding friction
rolling friction
drag

Answers

Answer:

Drag friction.

Explanation:

If you have a solid object, go through air, it experiences drag because the air molecules push back a tiny bit. This drag is enhanced because in water, the molecules are more resistant than air, that's why if you try to run in knee deep water, you experience much more drag than when you are running with your legs out of the water.

Physic its urgent1/ What is the total distance traveled by the object during the first 3 second

2/What is the average speed of the object during the following interval in t=6 sec and t= 8 sec

Answers

(1) Distance = speed × time

Total distance = 10m/sec × 3sec = 30m

(2) Average speed = (25m/sec + 10m/s) ÷ 2 = 17.5m/sec

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