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Alekssandra [29.7K]
2 years ago
12

Suzy drops a rock from the roof of her house. Mary sees the rock pass her 2.7 m tall window in 0.129 sec. From how high above th

e top of the window was the rock dropped? The acceleration of gravity is 9.8 m/s 2 . Answer in units of m.
Physics
1 answer:
vladimir1956 [14]2 years ago
8 0

Answer:

h = 22.35 m

Explanation:

given,

initial speed of the rock,u = 0 m/s

length of the window,l = 2.7 m

time taken to cross the window,t = 0.129 s

Speed of the rock when it crosses the window

v = \dfrac{l}{t}

v = \dfrac{2.7}{0.129}

  v = 20.93 m/s

height of the building above the window

using equation of motion

v² = u² + 2 g h

20.93² = 0² + 2 x 9.8 x h

h = 22.35 m

Hence, the height of the building above the top of window is equal to h = 22.35 m

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A mass M suspended by a spring with force constant k has aperiod T when set into oscillations on Earth. Its period on Mars,whose
olchik [2.2K]

Answer:

C)T

Explanation:

The period of a mass-spring system is:

T=2\pi\sqrt\frac{m}{k}

As can be seen, the period of this simple harmonic motion, does not depend at all on the gravitational acceleration (g), neither the mass nor the spring constant depends on this value.

6 0
3 years ago
Is there a "real" simple machine that has an efficiency of 100%?
VARVARA [1.3K]

Answer:

NO

Explanation:

No, a machine cannot be 100% efficient. This is due to the movement of the moving parts siding against each other and causing friction. This friction is the one that creates heat and causes wear and tear between moving ports f the machine hence making the machine to decrease in efficiency with time

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2 years ago
What is the meaning of viscosity?
Vera_Pavlovna [14]

the state of being thick, sticky, and semifluid in consistency, due to internal friction.

5 0
2 years ago
Alternating Current In Europe, the voltage of the alternating current coming through an electrical outlet can be modeled by the
stealth61 [152]

Answer:

\frac{50}{\pi }Hz

Explanation:

In alternating current (AC) circuits, voltage (V) oscillates in a sine wave pattern and has a general equation as a function of time (t) as follows;

V(t) = V sin (ωt + Ф)            -----------------(i)

Where;

V = amplitude value of the voltage

ω = angular frequency = 2 π f        [f = cyclic frequency or simply, frequency]

Ф = phase difference between voltage and current.

<u><em>Now,</em></u>

From the question,

V(t) = 230 sin (100t)              ---------------(ii)

<em><u>By comparing equations (i) and (ii) the following holds;</u></em>

V = 230

ω = 100

Ф = 0

<em><u>But;</u></em>

ω = 2 π f = 100

2 π f = 100             [divide both sides by 2]

π f = 50

f = \frac{50}{\pi }Hz

Therefore, the frequency of the voltage is \frac{50}{\pi }Hz

7 0
3 years ago
What is the maximum acceleration the belt can have without the crate slipping? express your answer using two significant figures
Montano1993 [528]

To prevent the crate from slipping, the maximum force that the belt can exert on the crate must be equal to the static friction force.


Ff = 0.5 * 16 * 9.8 = 78.4 N

a = 4.9 m/s^2


If acceleration of the belt exceeds the value determined in the previous question, what is the acceleration of the crate?


In this situation, the kinetic friction force is causing the crate to decelerate. So the net force on the crate is 78.4 N minus the kinetic friction force.


Ff = 0.28 * 16 * 9.8 = 43.904 N

Net force = 78.4 – 43.904 = 34.496 N

To determine the acceleration, divide by the mass of the crate.

a = 34.496 ÷ 16 = 2.156 m/s^2



8 0
3 years ago
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