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siniylev [52]
3 years ago
10

A boulder is raised above the ground, so that its potential energy relative to the ground is 200 J. Then it is dropped. Estimate

what its kinetic energy will be just before hitting the ground.
Physics
1 answer:
babymother [125]3 years ago
6 0

Answer:

200 J

Explanation:

In this problem, I assume there is no air resistance, so the  system is isolated (=no external forces).

For an isolated system, the total mechanical energy is constant, and it is given by:

E=KE+PE

where

KE is the kinetic energy

PE is the potential energy

The kinetic energy is the energy due to the motion of the object,  while the potential energy is the energy due to the position of the object relative to the ground.

At the beginning, when the boulder is raised above the ground, its height above the ground is maximum, while its  speed is zero; it means that all its mechanical energy is just potential energy, and it is:

E=PE_{max}=200 J

As the boulder falls  down, its altitude decreases, so its potential energy decreases, while the speed increases, and the kinetic energy increases. Therefore, potential energy is converted into kinetic energy.

Eventually, just before the boulder hits the ground, the height of the object is zero, and the speed is maximum; this means that all the energy has now converted into kinetic energy, and we have

E=KE_{max}=200 J

Therefore, the kinetic energy just before hitting the ground is 200 J.

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3 years ago
Suppose you are navigating a spacecraft far from other objects. The mass of the spacecraft is 2.0 104 kg (about 20 tons). The ro
elena-14-01-66 [18.8K]

Answer:

   r = <2.640 10⁶, 1.01 10⁸, 0> m

Explanation:

For this exercise we are going to solve it for each direction separately,

we locate a fixed reference frame in space at the height of the rocket, such that the position of the rocket is

  r₀ = <4, 4, 0> 10³ m

X axis

the initial velocity of the ship on this axis is v₀ₓ = 0, when it passes through the point x₀ = 4 km it ignites the rockets, experiencing a force of Fₓ = 7.0 10⁵ N for 21 s and the rockets turn off

They ask where it is after one hour t = 1 h = 3600 s

Let's apply Newton's second law

        Fₓ = m aₓ

        aₓ = Fₓ / m

        aₓ = 7.0 10⁵/2 10⁴

        aₓ = 3.5 10¹ m / s

Let's use kinematics to find the distance

for the first t₁ = 21 s the movement is accelerated

        x₁ = x₀ + v₀ t₁ + ½ aₓ t₁²

        x₁ = x₀ + ½ aₓ t₁²

        x₁ = 4000 + ½ 35 21² = 4000 + 7717,.5

        x₁ = 11717.5 m

this instant has a speed of

        vₓ = v₀ₓ + aₓ t

        vₓ = aₓ t ₁

        vₓ = 35  21

        vₓ = 735 m / s

the rest of the time there is no acceleration so it is uniform motion at this speed

        t₂ = 3600 - 21

        t₂ = 3576 s

         vₓ = x₂ / t₂

         x₂ = vₓ t₂

         x₂ = 735  3576

         x₂ = 2,628 10⁶ m

the total distance traveled in this direction is

         x_total = x₁ + x₂

         x_total = 11717.5 + 2.628 10⁶

         x_total = 2,640 10⁶ m

Y axis

on this axis it is in the initial position of y₀ = 4000 m, with an initial velocity of v_{oy} = 28 10³ m / s and there is no force on this axis F_{y} = 0

The movement in this axis is uniform,

       v_{y} = y / t

       y = v_{y} t

       y = 28 10³/3600

       y = 1.01 10⁸ m

the total distance is

       y_total = y₀ + y

       y_total = 4000 + 1.01 10⁸

       y_total = 1.01 10⁸ m

Z axis

the initial position is z₀ = 0, with an initial velocity of v₀ = 0 and in this axis there is no force F_{z} = 0

the movement is uniform

         z = 0

the final position of the rocket after 1 h is

      r = <2.640 10⁶, 1.01 10⁸, 0> m

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Answer:

9)a

10) I think true

11)b

Explanation:

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10) if a moving object has a change of speed or direction, it would have an acceleration. now if a moving object experiences an unbalanced force, it'd either slow down, gain speed or change direction, and in all of the three possibilities it'd have an acceleration.

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and the rightward force is 5N more than the leftward force. so the Net Force would be 5N.

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if it is unclear or you need more explanation, ask freely.

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3 years ago
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Ksju [112]

Answer:

17. NADH has a molar extinction coefficient of 6200 M2 cm at 340 nm. Calculate the molar concentration of NADH required to obtain an absorbance of 0.1 at 340 nm in a 1-cm path length cuvette. 18. A sample with a path length of 1 cm absorbs 99.0% of the incident light at a wavelength of 274 nm, measured with respect to an appropriate solvent blank. Tyrosine is known to be the only chromophore present in the sample that has significant absorption at 274 nm. Calculate the molar concentration of tyrosine in the sample.

Explanation:

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2 years ago
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dangina [55]
Vector it always consists to size(magnitude) and direction 
8 0
3 years ago
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