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3 years ago

Explain why a reference points that are stationary are usually chosen to determine whether an object is in motion.

1 answer:

4 0

Answer: Stationary reference points are used to determine if a object is in motion because if the reference point is still,you will be able to see if the object is in motion. If you had a reference point that wasn't stationary, you wouldn't be able to tell if the object was in motion.

Explanation:

Stationary reference points are used to determine if a object is in motion because if the reference point is still,you will be able to see if the object is in motion. If you had a reference point that wasn't stationary, you wouldn't be able to tell if the object was in motion.

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An open container holds ice of mass 0.555 kg at a temperature of -16.6 ∘C . The mass of the container can be ignored. Heat is su

s2008m [1.1K]

Answer: A. 23.59 minutes.

B. 249.65 minutes

Explanation: This question involves the concept of Latent Heat and specific heat capacities of water in solid phase.

Latent heat of fusion is the total amount of heat rejected from the unit mass of water at 0 degree Celsius to convert completely into ice of 0 degree Celsius (and the heat required for vice-versa process).

Specific heat capacity of a substance is the amount of heat required by the unit mass of a substance to raise its temperature by 1 kelvin.

Here, given that:

mass of ice, m= 0.555 kg

temperature of ice, T= -16.6°C

rate of heat transfer, $q=820 J.min^{-1}$

specific heat of ice, $c_{i}= 2100 J.kg^{-1}.K^{-1}$

latent heat of fusion of ice, $L_{i}=334\times10^{3}J.kg^{-1}$

Asked:

1. Time require for the ice to start melting.

2. Time required to raise the temperature above freezing point.

Sol.: 1.

We have the formula:

$Q=mc\Delta T$

Using above equation we find the total heat required to bring the ice from -16.6°C to 0°C.

$Q= 0.555\times2100\times16.6$

$Q= 19347.3 J$

Now, we require 19347.3 joules of heat to bring the ice to 0°C and then on further addition of heat it starts melting.

∴The time required before the ice starts to melt is the time required to bring the ice to 0°C.

$t=\frac{Q}{q}$

$=\frac{19347.3}{820}$

= 23.59 minutes.

Sol.: 2.

Next we need to find the time it takes before the temperature rises above freezing from the time when heating begins.

Now comes the concept of Latent heat into the play, the temperature does not starts rising for the ice as soon as it reaches at 0°C it takes significant amount of time to raise the temperature because the heat energy is being used to convert the phase of the water molecules from solid to liquid.

From the above solution we have concluded that 23.59 minutes is required for the given ice to come to 0°C, now we need some extra amount of energy to convert this ice to liquid water of 0°C.

We have the equation: latent heat, $Q_{L}= mL_{i}$

$Q_{L}= 0.555\times334\times10^{3}= 185370 J$

Now the time required for supply of 185370 J:

$t=\frac{Q_{L}}{q}$

$t=\frac{185370}{820}$

t= 226.06 minutes

∴ The time it takes before the temperature rises above freezing from the time when heating begins= 226.06 + 23.59

= 249.65 minutes

8 0

3 years ago

A book is sitting on a table. Which of the following is true about the table? O A. It is pushing up on the book. O B. It exerts

777dan777 [17]

Answer:

yes it does exert a force, it pushes it up

Explanation:

this is called normal force

if it didn't exert a force the book would keep going down

according to newton every force has an equal amd opposite reaction

so the book exerts a force on the table and vice versa

hope this helped

5 0

3 years ago

As capacitor was discharging, what did you observe about q on its plates and the motion of charges in the external circuit?

liubo4ka [24]

As capacitor was discharging, The charge on the plate got reversed and the motion of charge is opposite to the flow of current.

The charging contemporary asymptotically processes 0 as the capacitor becomes charged up to the battery voltage.

The capacitor is completely charged when the voltage of the electricity supply is equal to that at the capacitor terminals. that is referred to as capacitor charging; and the charging segment is over when modern-day stops flowing thru the electrical circuit.

A capacitor can be slowly charged to the important voltage and then discharged quick to provide the power wanted. it's far even viable to charge several capacitors to a positive voltage and then discharge them in any such way as to get extra voltage out of the gadget than became installed.

Learn more about capacitor here:-brainly.com/question/14883923

#SPJ4

8 0

2 years ago

Barnacles are a type of arthropod in the subphylum Crustacea, and are related to crabs and lobsters. Barnacles are exclusively m

Contact [7]

The answer is commensalism because commensalism is a relationship where an organism is benefitted and the other is neither benefitted nor harmed. The barnacle is being benefited and the whale is not being benefited or harmed.

8 0

3 years ago

Read 2 more answers

A runner is jogging in a straight line at a

soldi70 [24.7K]

Answer:

13 km

Explanation:

The bird flies from the runner, to the finish line, and back to the runner. We can write two equations for the distance it travels:

d = 7.8 km + 7.8 km − 4.9 km/hr × t

d = 24.5 km/hr × t

Solve for t in the second equation and substitute into the first:

t = d / 24.5

d = 7.8 + 7.8 − 4.9 (d / 24.5)

d = 15.6 − 0.2 d

1.2 d = 15.6

d = 13

The bird flies a cumulative distance of 13 km.

4 0

3 years ago