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3 years ago

What does a measured number tell you?

Physics

1 answer:

oksano4ka [1.4K]3 years ago

5 0

Answer:

The precision at which the number was measured

Explanation:

The number of digits that you use to record a measurement indicates the precision of the measurement.

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You carry a 5 kg sack of potatoes across the store for 5 minutes, and you wait in line holding it for 30 seconds before you get

ludmilkaskok [199]

Answer:

The only work done is when the person lifts the sack over a distance, W = 78.48 [N]

Explanation:

We have to remember the definition of work, which tells us that work is the result of a force by a distance, we must apply this concept in each of the movements of the person in the problem described.

W = F * d

where:

F = force [N]

d = distance [m]

The force is given by the producto of the mass by the gravity.

F = 5 * 9.81 = 49.05 [N]

W = 49.05 * 1.6 = 78.48 [N]

3 0

3 years ago

A spring gun is made by compressing a spring in a tube and then latching the spring at the compressed position. A 4.97-g pellet

dimaraw [331]

Answer:

$v = 2.8898 \frac{m}{s}$

Explanation:

This is a problem easily solve using energy conservation. As there are no non-conservative forces, we know that the energy is conserved.

When the spring is compressed downward, the spring has elastic potential energy. When the spring is relaxed, there is no elastic potential energy, but the pellet will have gained gravitational potential energy and kinetic energy. Lets see what are the terms for each of this.

<h3>Elastic potential energy</h3>

We know that a spring following Hooke's Law has a elastic potential energy:

$E_{ep} = \frac{1}{2} k (\Delta x)^2$

where $\Delta x$ is the displacement from the relaxed length and k is the spring's constant.

To obtain the spring's constant, we know that Hooke's law states that the force made by the spring is :

$\vec{F} = - k \Delta \vec{x}$

as we need 9.12 N to compress 4.60 cm, this means:

$k = \frac{9.12 \ N}{4.6 \ 10^{-2} \ m}$

$k = 198.26 \ \frac{ N}{m}$

So, the elastic energy of the compressed spring is:

$E_{ep} = \frac{1}{2} 198.26 \ \frac{ N}{m} (4.6 \ 10^{-2} \ m)^2$

$E_{ep} = 0.209759 \ Joules$

And when the spring is relaxed, the elastic potential energy will be zero.

<h3>Gravitational potential energy</h3>

To see how much gravitational potential energy will the pellet win, we can use

$\Delta E_{gp} = m g \Delta h$

where m is the mass of the pellet, g is the acceleration due to gravity and \Delta h is the difference in height.

Taking all this together, the gravitational potential energy when the spring is relaxed will be:

$\Delta E_{gp} = 4.97 \ 10^{-3} kg \ 9.8 \frac{m}{s^2} 4.6 \ 10^{-2} m$

$\Delta E_{gp} = 0.00224 \ Joules$

<h3>Kinetic Energy</h3>

We know that the kinetic energy for a mass m moving at speed v is:

$E_k = \frac{1}{2} m v^2$

so, for the pellet will be

$E_k = \frac{1}{2} \ 4.97 \ 10^{-3} kg \ v^2$

<h3>All together</h3>

By conservation of energy, we know:

$E_{ep} = \Delta E_{gp} + E_k$

$0.209759 \ Joules = 0.00224 \ Joules + \frac{1}{2} \ 4.97 \ 10^{-3} kg \ v^2$

$\frac{1}{2} \ 4.97 \ 10^{-3} kg \ v^2 = 0.209759 \ Joules - 0.00224 \ Joules$

$\frac{1}{2} \ 4.97 \ 10^{-3} kg \ v^2 = 0.207519 \ Joules$

$v = \sqrt{ \frac{ 0.207519 \ Joules}{ \frac{1}{2} \ 4.97 \ 10^{-3} kg } }$

$v = 2.8898 \frac{m}{s}$

7 0

3 years ago

Identify and define the four major forms of matter, explain how melting, freezing, boiling,

mina [271]

There are four forms of matter: Solid, Liquid, gas and Plasma and matter undergoes various state changes termed as melting, freezing, boiling, evaporation, condensation, sublimation and deposition.

<u>Explanation:</u>

Solids

A matter that have a definite shape because of its closely packed molecular structure; are known as Solids. It can be identified as they have a definite shape and cannot flow or float without external forces are applied.

Liquids

These have a an internal molecular structure with comparatively more spaces with one another. Liquids have a property to flow and change shape according to the container it is taken.

Gases

The internal molecular structure of gases has the widest range of space among one another and thus they have a floating property because of least density.

Plasma

A complete ionized gas which has equal amount of positively and negatively charged ions. The best example of plasma is a plasma-ball.

<u>Phase transformation among the four forms of matter</u>

<u>Melting</u>

A matter changing from a solid phase to liquid phase is known as melting. Ex: Ice into water

<u>Freezing</u>

A matter changing from liquid to solid is known as freezing.

<u>Boiling</u>

When the liquid is heated to its boiling point, this gets transformed into the state of gas where liquid's pressure equals to the external pressure.

<u>Evaporation</u>

Once the liquid reached the temperature range above the boiling point ad starts converting into vapours or gaseous state.

<u>Condensation</u>

When the gases changes from the gaseous phase to liquid phase, this is called condensation.

<u>Sublimation</u>

The change of solid into gas is called as sublimation.

<u>Deposition</u>

Deposition refers the thermodynamic process where phase transition takes place as the gas solidifies without passing through the liquid phase. An example: the process of converting water vapour from frozen air directly into ice without initially becoming a liquid.

3 0

3 years ago

1) Which of the following statements about physical models is not true?

Alex_Xolod [135]

1. "<span>Physical models are usually in the form of a graph" is the statement among the statements given about physical models that is not true. The correct option among all the options that are given in the question is the third option or option "c".

2. "Predicting weather patterns" is the one among the following scenarios that </span>represents the best use of a scientific model. <span>The correct option among all the options that are given in the question is the first option or option "a".</span>

8 0

3 years ago

Suppose you have two solid bars, both with square cross-sections of 1 cm2. They are both 24.6 cm long, but one is made of copper

vodka [1.7K]

Explanation:

Expression to calculate thermal resistance for iron ( $R_{I}$ ) is as follows.