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Lunna [17]
3 years ago
14

A rock hits the ground at a speed of 15 m/s and leaves a hole 50 cm deep. After it hits the ground, what is the magnitude of the

rock's (Assumed)uniform acceleration? A) 112.5 m/s^2
B) 225 m/s^2
C) 225
D) 127.5 m/s^2
Physics
1 answer:
garik1379 [7]3 years ago
4 0

Answer:

B) 225 m/s^2

Explanation:

The rock hits the ground at 15m/s and travels 50cm=0.5m through the ground until it stops.

The acceleration is supposed to be uniform, so the formula we have to use is v^2=v_0^2+2ad, which for acceleration is:

a=\frac{v^2-v_0^2}{2d}

Taking the <em>downwards direction as positive</em> (the direction of traveling, so the initial velocity and displacement will be positive), substituting our values for that movement we have:

a=\frac{v^2-v_0^2}{2d}=\frac{(0m/s)^2-(15m/s)^2}{2(0.5m)}=-255m/s^2

Where the <em>negative sign indicates that it is pointing upwards.</em>

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A 300-kg piano being held by a crane is accidentally dropped from a height of 15 meters. a. What is the speed of the piano just
FinnZ [79.3K]

Answer:

a) 17.16m/s

b) 44,145J

c) Sound the piano makes when hitting the ground, vibration of the ground, heat.

d) i) It's smaller due to the energy dissipated by the friction between air and the parachute.

ii) It stays the same, the only difference is that the dissipated energy is distributed between air resistance and the kinetic energy dissipated by the ground whent he piano hits it.

Explanation:

a)

In order to solve this problem we must start by doing a drawing of the situation, which will help us visualize the problem better. (See attached picture).

So, in this problem we can ignore air resistance so we can say that the energy is conserved, this is the total initial energy is the same as the total final energy, so we get that:

U_{0}+K_{0}=U_{f}+K_{f}

When the piano is released it has an initial speed of zero, so the initial kinetic energy is zero. When the piano hits the ground it will have a height of 0m, so the final potential energy is zero as well. This will simplify our equation:

U_{0}=K_{f}

We know that potential energy is given by the formula:

U=mgh

and kinetic energy is given by the formula:

K=\frac{1}{2}mv^{2}

which can be substituted in our equation:

mgh=\frac{1}{2}mv^{2}

we can divide both sides of the equation into the mass of the piano, so we get:

gh=\frac{1}{2}v^{2}

which can be solved for the final velocity which yields:

v=\sqrt{2gh}

we can now substitute the data provided by the problem so we get:

v=\sqrt{2(9.81m/s^{2})(15m)}

which yields:

v=17.16m/s

b)

Since energy is conserved, this means that the total dissipated energy will be the same as the potential energy, so we get that:

E=mgh

so

E=(300kg)(9.81m/s^{2})(15m)

which yields:

E=44,145J

c)

When the piano hits the ground, the kinetic energy it had will be transformed to other types of energy, mostly vibration and heat. The vibration will turn to sound due to the movement of air created by the piano itself and the ground. And heat is created by the friction between the molecules created by the vibrations and the collition itself. So some of the indicators of this release of energy could be:

-Sound

-Vibration

-Heat.

d)

i) The amount of inetic energy dissipated would decrease due to the friction between air and the parachute. Since air is resisting the movement of the piano, this will translate into a loss of energy, if we did an energy balance we would get that:

U_{0}=K_{f}+E_{p}

The total amount of energy is conserved but it will be distributed between the energy lost due to air resistance and the kinetic energy the piano has at the time it hits the ground.

ii) So the total amount of energy dissipated remains the same, the only difference is that it will be distributed between air resistance and the kinetic energy of the piano.

3 0
3 years ago
Pls quickly brainliest to the first to anwser
fiasKO [112]

Answer:

8m/s^2

Explanation:

hope it helps........

4 0
2 years ago
Read 2 more answers
3. What is electric current?<br> The flow of moving electrons<br><br> electrons that move one time
3241004551 [841]

Answer:

An electric current is a stream of charged particles, such as electrons or ions, moving through an electrical conductor or space. It is measured as the net rate of flow of electric charge through a surface or into a control volume. ... In electric circuits the charge carriers are often electrons moving through a wire.

7 0
3 years ago
Read 2 more answers
A type of Lead (Pb) ion has a + 4 oxidation number. Sulfur (S) has a — 2 oxidation number. What would be the chemical formula fo
serious [3.7K]

Answer: The chemical formula for the compound of these two elements is PbS_2

Explanation:

For formation of a neutral ionic compound, the charges on cation and anion must be balanced. The cation is formed by loss of electrons by metals and anions are formed by gain of electrons by non metals.

Here metal lead is having an oxidation state of +4 called as Pb^{4+} cation and sulphur non metal has oxidation state of -2 called as S^{2-}. Thus they combine and their oxidation states are exchanged and written in simplest whole number ratios to give neutral PbS_2

The chemical formula for the compound of these two elements is PbS_2

4 0
3 years ago
A 126- kg astronaut (including space suit) acquires a speed of 2.70 m/s by pushing off with her legs from a 1800-kg space capsul
jeka94

The change in the speed of the space capsule will be -0.189 m/s.

The average force exerted by each on the other will be 567 N.

The kinetic energy of each after the push for the astronaut and the capsule are 459.27 J and 32.14 J.

<h3>Given:</h3>

Mass of the astronaut, m_a = 126 kg

Speed he acquires, v_{a}  = 2.70 m/s

Mass of the space capsule, m_{c} = 1800kg

The initial momentum of the astronaut-capsule system is zero due to rest.

P_f = m_av_a + m_cv_c

P_I = 0

m_av_a + m_cv_c = 0

v_c =\frac{- m_a v_a}{m_c}}\\\\

   = \frac{126* 2.70}{1800}

   = - 0.189 m/s

Therefore,

According, to the impulse-momentum theorem;

FΔt = ΔP

ΔP = m Δv

ΔP = 126×2.70

    = 340.2 kgm/sec

t is time interval = 0.600s

F = ΔP/Δt

F = 340.2/0.600

  = 567 N

Therefore, the average force exerted by each on the other will be 567 N.

The Kinetic Energy of the astronaut;

K.E = \frac{1}{2} m v^2

     = \frac{1}{2} × 126 × (2.70) ^2

     = 459.27 J

The Kinetic Energy of the capsule;

K.E = \frac{1}{2} m v^2

     = \frac{1}{2}×1800×(0.189) ^2

     = 32.14 J

Therefore, the kinetic energy of each after the push for the astronaut and the capsule are 459.27 J and 32.14 J.

Learn more about kinetic energy here:

brainly.com/question/26520543

#SPJ1

3 0
1 year ago
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