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3 years ago

Alexander calders mobiles, like untitled, move when air currents move through them, making them_____________

1 answer:

4 0

Alexander Calders mobiles, like untitled, move when air currents move through them, making them kinetic. Alexander Calder was an American artist, famous for his abstract sculpture, hanging mobiles, and Kinetic art. Kinetic art is the <span>art that depends on motion for its effect. The kinetic art's works of Alexander Calders were called "mobiles".</span>

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4. A driver travels 135 km, east in 1.5 h, stops for 45 minutes for lunch,

stira [4]

Answer:

The driver's average velocity is 82.35 km/h.

Explanation:

Given:

The motion of the driver can be divided into 3 parts:

i. Displacement of the driver in 1.5 hours = 135 km

ii. Rest for 45 minutes.

iii. Displacement in next 2 hours = 215 km

The direction of motion remains same (east).

Now, total displacement of the driver is, $D_{Total}=135+215=350$ km.

Rest time is 45 minutes. Converting it to hours, we need to use the conversion factor $1\textrm{ min} = \frac{1}{60}$ hour.

So, 45 minutes in hours is equal to $\frac{45}{60}=0.75$ hours.

Now, total time taken for the complete journey is, $\Delta t=1.5+\frac{45}{60}+2=1.5+0.75+2=4.25\textrm{ h}$

Average velocity is given as:

$v_{avg}=\frac{\textrm{Total displacement}}{Total time}=\frac{350}{4.25}=82.35\textrm{ km/h}$

Therefore, the driver's average velocity is 82.35 km/h

4 0

3 years ago

What is the relationship between mass and acceleration on an object when the force is held constant?

Andreyy89

Answer:

according to newtons second law of motion,

Force = mass * acceleration

The acceleration of the body is directly proportional to the net force acting on the body and inversely proportional to the mass of the body.

I. e mass and acceleration are directly proportional to each other.

8 0

3 years ago

A pencil rolls horizontally of a 1 meter high desk and lands .25 meters from the base of the desk. How fast was the pencil rolli

vovikov84 [41]

Answer: 0.55 m/s

Explanation:

This situation is related to projectile motion (also called parabolic motion), where the main equations are as follows:

$x=V_{o} cos\theta t$ (1)

$y=y_{o}+Vo sin \theta t + \frac{g}{2}t^{2}$ (2)

Where:

$x=0.25 m$ is the horizontal displacement of the pencil

$V_{o}$ is the pencil's initial velocity

$\theta=0\°$ since we are told the pencil rolls <u>horizontally</u> before falling

$t$ is the time since the pencil falls until it hits the ground

$y_{o}=1 m$ is the initial height of the pencil

$y=0$ is the final height of the pencil (when it finally hits the ground)

$g=-9.8m/s^{2}$ is the acceleration due gravity, always acting vertically downwards

Begining with (1):

$x=V_{o} cos(0\°) t$ (3)

$x=V_{o}t$ (4)

Finding $t$ from (2):

$0=1 m+ \frac{-9.8m/s^{2}}{2}t^{2}$ (5)

$t=\sqrt{\frac{-2y_{o}}{g}}$ (6)

Substituting (6) in (4):

$x=V_{o}\sqrt{\frac{-2y_{o}}{g}}$ (7)

Isolating $V_{o}$ :

$V_{o}=\frac{x}{\sqrt{\frac{-2y_{o}}{g}}}$ (8)

$V_{o}=\frac{0.25 m}{\sqrt{\frac{-2(1 m)}{-9.8m/s^{2}}}}$ (9)

Finally:

$V_{o}=0.55 m/s$

4 0

3 years ago

A 10kg box accelerates forward at a rate of 12 m/s^2. What is the force acting on the box?

Allushta [10]

Answer:

120N

Explanation:

Newton's second law formula: F= ma

given that m = 10 kg, a = 12 m/s^2

F = ma = 10 kg * 12 m/s^2 = 120 kgm/s^2 = 120 N

5 0

2 years ago

An electron accelerates through a 12.5 V potential difference, starting from rest, and then collides with a hydrogen atom, excit

Yanka [14]

Answer:

Initial state Final state

3 ⇒ 2

3 ⇒ 1

2 ⇒ 1

Explanation:

For this exercise we must use Bohr's atomic model

E = - 13.606 / n²

where is the value of 13.606 eV is the energy of the ground state and n is the integer.

The energy acquired by the electron in units of electron volt (eV)

E = e V

E = 12.5 eV

all this energy is used to transfer an electron from the ground state to an excited state

ΔE = 13.6060 (1 / n₀² - 1 / n²)

the ground state has n₀ = 1

ΔE = 13.606 (1 - 1/n²)

1 /n² = 1 - ΔE/13,606

1 / n² = 1 - 12.5 / 13.606

1 / n² = 0.08129

n = √(1 / 0.08129)

n = 3.5

since n is an integer, maximun is

n = 3

because it cannot give more energy than the electron has

From this level there can be transition to reach the base state.

Initial state Final state

3 ⇒ 2

3 ⇒ 1

2 ⇒ 1

8 0

3 years ago