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3 years ago

Which of these is an example of physical change?

2 answers:

8 0

That will be A melting a substance that's because the rest are examples of chemical changes and also its the same thing but in a different form.

aleksandrvk [35]3 years ago

7 0

Answer:

Melting a substance

Explanation:

Melting a substance is a physical change. It is a physical change because the process is irreversible that is the product after the substance is melted can be converted back to its original state.

Taking ice as an example, ice being a solid matter can be melted by applying heat. This melted ice will change to water. The water which is the product formed can be freezed to change it back to its initial state which is ice. Hence melting is a physical change.

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Un autocar que circula a 81 km/h frena uniformemente con una aceleración de -4,5 m/s2.

horsena [70]

Answer:

a) $\Delta x=56.25 m$

b) imagen adjunta

Explanation:

a) Primero debemos hacer la conversión de 81 km/h a m/s, esto es 22.5 m/s.

Ahora, usando la ecuacion cinemática, en un movimiento acelerado tenemos:

$v_{f}^{2}=v_{0}^{2}+2a \Delta x$

Queremos encontrar la posición hasta detenerse, osea vf = 0.

$\Delta x=\frac{-v_{0}^{2}}{2a}$

$\Delta x=\frac{-22.5^{2}}{-2*4.5}$

$\Delta x=56.25 m$

b) Para este caso el gráfico se encuentra adjunto.

Espero que te sirva de ayuda!

Download pdf

8 0

3 years ago

Problem page a cyclist traveled 20 kilometers per hour faster than an in-line skater. in the time it took the cyclist to travel

RideAnS [48]

<span>Answer: skater x km/h cyclist 20 faster x + 20 km/h skater 30 km cyclist 80 km skater time = cyclist time t=d/r 30 / x = 80 /( x + 20 cross multiply 30 ( x + 20 ) = 80 x 30 x + 600 = 80 x 30 x - 80 x = -600 -50 x = -600 / -50 x = 12 km/h 12 km/h skater</span>

3 0

3 years ago

A ball is thrown directly downward with an initial speed of 7.70 m/s, from a height of 30.2 m. After what time interval does it

KatRina [158]

Answer:

$t = 1.82$

Explanation:

Given

$u = 7.70m/s$ -- initial velocity

$s = 30.2m$ --- height

Required

Determine the time to hit the ground

This will be solved using the following motion equation.

$s = ut + \frac{1}{2}gt^2$

Where

$g = 9,8m/s^2$

So, we have:

$30.2 = 7.70t + \frac{1}{2} * 9.8 * t^2$

$30.2 = 7.70t + 4.9 * t^2$

Subtract 30.2 from both sides

$30.2 -30.2 = 7.70t + 4.9 * t^2 - 30.2$

$0 = 7.70t + 4.9 * t^2 - 30.2$

$0 = 7.70t + 4.9t^2 - 30.2$

$7.70t + 4.9t^2 - 30.2 = 0$

$4.9t^2 + 7.70t - 30.2 = 0$

Solve using quadratic formula:

$t = \frac{-b\±\sqrt{b^2 - 4ac}}{2a}$

Where

$a = 4.9;\ b = 7.70;\ c = -30.2$

$t = \frac{-7.70\±\sqrt{7.70^2 - 4*4.9*-30.2}}{2*4.9}$

$t = \frac{-7.70\±\sqrt{651.21}}{9.8}$

$t = \frac{-7.70\±25.52}{9.8}$

Split the expression

$t = \frac{-7.70+25.52}{9.8}$ or $t = \frac{-7.70-25.52}{9.8}$

$t = \frac{17.82}{9.8}$ or $t = -\frac{33.22}{9.8}$

Time can't be negative; So, we have:

$t = \frac{17.82}{9.8}$

$t = 1.82$

Hence, the time to hit the ground is 1.82 seconds

7 0

2 years ago

How does changing the potential difference in a circuit affect the current and the resistance?

Effectus [21]

Answer:

The current will be increased and also for the resistance.

Explanation:

The analysis of a direct current circuit can give us the explanation we need. Using the ohm law, which tells us that the voltage is equal to the product of the current by the resistance we have:

$V=I*R\\where\\V= voltage [V]\\I= amperes [amp]\\R=resistance [ohm]\\$

The voltage is equal to the potential difference therefore we will have these expressions:

$I=\frac{V}{R} \\R= \frac{V}{I}$

If we increase the potential differential or circuit voltage, the current will also increase and so does the resistance by increasing the voltage. If we put numerical values in the equation given before, we can confirm this fact.

4 0

3 years ago

See how a block and tackle system can increase your mechanical advantage. You will need two broomsticks, a rope, and two helpers

Lisa [10]

Answer:

You are the one who will answer that because you will experiment

4 0

3 years ago