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Y_Kistochka [10]

3 years ago

13

A 38.0 kg child is in a swing that is attached to ropes 1.70 m long. The acceleration of gravity is 9.81 m/s 2 . Find the gravit

ational potential energy associated with the child relative to the child’s lowest position under the following conditions:

1 answer:

siniylev [52]3 years ago

7 0

Answer:

at zero point : GPE = 0 J

at max height : GPE = 633.7 J

Explanation:

the gravitational potential energy at the lowest point is zero

maximum height relative to the lowest point = h =1.70 m

G potential energy at max height = mgh = (38kg)(9.81m/s^2)(1.7)

= 633.7 J

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Identify the situations that have an unbalanced force. Check all that apply. A baseball speeds up as it falls through the air. A

viktelen [127]

<span>A baseball speeds up as it falls through the air.
Yes. Forces on the balloon are unbalanced.
The balloon is speeding up, so we know that the downward force
of gravity is stronger than the upward force of air resistance.

A soccer ball is at rest on the ground.
No. The ball is not accelerating, so we know that the forces on it
are balanced.
The downward force of gravity on the ball and the upward force
of the ground are equal.

An ice skater glides in a straight line at a constant speed.
No. The skater's speed and direction are not changing, so he is not
accelerating. That tells us that the forces on him are balanced.

A bumper car hit by another car moves off at an angle.
Yes. The direction in which the car was moving changed.
That's acceleration, so we know that the forces on it are unbalanced,
at least at the moment of impact.

A balloon flies across the room when the air is released.
Yes. The balloon was not moving. But when the little nozzle was
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5 0

3 years ago

Read 2 more answers

The temperature at 8:00

musickatia [10]

Change in temperature = final temperature - Initial temperature
Δt = t₂ - t₁
Δt = 17 - (-6)
Δt = 17 + 6 = 23 f

In short, Your Answer would be Option D

Hope this helps!

6 0

3 years ago

A beam of light strikes a sheet of glass at an angle of 57.0° with the normal in air. You observe that red light makes an angle

Contact [7]

<h2>Answers: </h2>

1) 1.359, 1.403

2) $2.207(10)^{8}m/s$ , $2.138(10)^{8}m/s$

Explanation:

The described situation is known as Refraction.

Refraction is a phenomenon in which a wave (the light in this case) bends or changes it direction when passing through a medium with a refractive index different from the other medium.

In this context, the Refractive index $n$ is a number that describes how fast light propagates through a medium or material, and is defined as the relation between the speed of light in vacuum ( $c=3(10)^{8}m/s$ ) and the speed of light $v$ in the second medium:

$n=\frac{c}{v}$ (1)

On the other hand we have the Snell’s Law:

$n_{1}sin(\theta_{1})=n_{2}sin(\theta_{2})$ (2)

Where:

$n_{1}$ is the first medium refractive index . We are told is the air, hence $n_{1}\approx 1$

$n_{2}$ is the second medium refractive index

$\theta_{1}$ is the angle of the incident ray

$\theta_{2}$ is the angle of the refracted ray

Knowing this, let's begin with the answers:

<h2><u>1) Indexes of refraction for red and violet light</u></h2><h2 /><h2>1a) Red light</h2>

Using equation (2) according to Snell's Law and $\theta_{1}=57.0\º$ $\theta_{2}=38.1\º$ :

$(1)sin(57.0\º)=n_{2}sin(38.1\º)$

Finding $n_{2}$ :

$n_{2}=\frac{sin(57.0\º)}{sin(38.1\º)}$

$n_{2}=1.359$ (3)>>>Index of Refraction for red light

<h2>1b) Violet light</h2>

Again, using equation (2) according to Snell's Law and $\theta_{1}=57.0\º$ $\theta_{2}=36.7\º$ :

$(1)sin(57.0\º)=n_{2}sin(36.7\º)$

Finding $n_{2}$ :

$n_{2}=\frac{sin(57.0\º)}{sin(36.7\º)}$

$n_{2}=1.403$ (4) >>>Index of Refraction for violet light

<h2><u>2) Speeds of red and violet light</u></h2><h2 /><h2>1a) Red light</h2>

Here we are going to use equation (1):

$n_{red}=\frac{c}{v_{red}}$

$v_{red}=\frac{c}{n_{red}}$

Substituting (3) in this equation:

$v_{red}=\frac{3(10)^{8}m/s}{1.359}$

$v_{red}=2.207(10)^{8}m/s$ >>>>Speed of red light

<h2>1a) Violet light</h2>

Using again equation (1):

$n_{violet}=\frac{c}{v_{violet}}$

$v_{violet}=\frac{c}{n_{violet}}$

Substituting (4) in this equation:

$v_{violet}=\frac{3(10)^{8}m/s}{1.403}$

$v_{red}=2.138(10)^{8}m/s$ >>>>Speed of violet light

3 0

3 years ago

They are adding steel components to the roof supports of the structure. We know that steel elongates when heated. At what temper

Andru [333]

Answer:

The change in temperature of 576.9°C will produce an elongation of 9 inches per feet in steel.

Explanation:

The formula for linear expansion of a material is:

ΔL = αLΔT

where, ΔL = change in length

L = Original length

ΔT = Change in temperature

α = coefficient of linear expansion

For steel, α = 13 x 10^-6 /°C

L = 100 ft

ΔL = (9 in)(1 ft/12 in) = 0.75 ft

Therefore,

0.75 ft = (13 x 10^-6 /°C)(100 ft)ΔT

<u>ΔT = 576.9°C</u>

<u></u>

8 0

3 years ago

Additional Problem: A simple pendulum, consisting of a string (of negligible mass) of length L with a small mass m at the end, i

kykrilka [37]

Answer:

a) v = √ 2gL abd b) θ = 45º

Explanation:

a) for this part we use the law of conservation of energy,

Highest starting point

Em₀ = U = mg h

Final point. Lower

Em₂ = ½ m v²

Em₀ = Em₂

m g h = ½ m v²

v = √2g h

v = √ 2gL

b) the definition of power is the relationship between work and time, but work is the product of force by displacement

P = W / t = F. d / t = F. v

If we use Newton's second law, with one axis of the tangential reference system to the trajectory and the other perpendicular, in the direction of the rope, the only force we have to break down is the weight

sin θ = Wt / W

Wt = W sin θ

This force is parallel to the movement and also to the speed, whereby the scalar product is reduced to the ordinary product

P = F v

The equation that describes the pendulum's motion is

θ = θ₀ cos (wt)

Let's replace

P = (W sin θ) θ₀ cos (wt)

P = W θ₀ sint θ cos (wt)

We use the equation of rotational kinematics

θ = wt

P = Wθ₀ sin θ cos θ

Let's use

sin 2θ = 2 sin θ cos θ

P = Wθ₀/2 sin 2θ

This expression is maximum when the sine has a value of one (sin 2θ = 1), which occurs for 90º,

2θ = 90

θ = 45º

5 0

3 years ago