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yanalaym [24]
3 years ago
6

A small rock is thrown vertically upward with a speed of 27.0 m/s from the edge of the roof of a 21.0-m-tall building. The rock

doesn't hit the building on its way back down and lands in the street below. Ignore air resistance. Part A: What is the speed of the rock just before it hits the street?
Part B: How much time elapses from when the rock is thrown until it hits the street?
Physics
1 answer:
lbvjy [14]3 years ago
8 0

Answer:

A. 33.77 m/s

B. 6.20 s

Explanation:

Frame of reference:

Gravity g=-9.8 m/s^2; Initial position (roof) y=0; Final Position street y= -21 m

Initial velocity upwards v= 27 m/s

Part A. Using kinematics expression for velocities and distance:

V_{final}^{2}=V_{initial}^{2}+2g(y_{final}-y_{initial})\\V_{f}^{2}=27^{2}-2*9.8(-21-0)=33.77 m/s

Part B. Using Kinematics expression for distance, time and initial velocity

y_{final}=y_{initial}+V_{initial}t+\frac{1}{2} g*t^{2}\\==> -0.5*9.8t^{2}+27t+21=0\\==> t_1 =-0.69 s\\t_2=6.20 s

Since it is a second order equation for time, we solved it with a calculator. We pick the positive solution.

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The correct answer is: waxing gibbous, 3 days

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Waning quarter moon: hair removal time and bangs cuts.

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6 0
3 years ago
What is a sedimentary, igneous, and a metamorphic rock?
Tanya [424]

Answer:

Igneous rock , formed by the cooling of magma (molten rock) inside the Earth or on the surface. Sedimentary rocks, formed from the products of weathering by cementation or precipitation on the Earth's surface. Metamorphic rocks, formed by temperature and pressure changes inside the Earth.

Explanation:

The information was found on:

https://msnucleus.org/membership/html/k-6/rc/rocks/3/rcr3_1a.html

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Two objects are moving at equal speed along a level, frictionless surface. the second object has twice the mass of the first obj
lbvjy [14]

Answer:

They both rises to same height.

Explanation:

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mgH=\frac{1}{2}mv^{2}\\ v=\sqrt{2gH}

Here, m is the mass, v is the velocity, g is the acceleration due to gravity and H is the height.

Here the height is independent on the mass of an object and its only depend on velocity.

Now according to the question, two objects have same velocity but they have different masses.

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8 0
3 years ago
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sweet [91]

Answer:

37.33m

Explanation:

Using the equation of motion

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S = 0 + 1/2(9.8)(2.76)^2

S = 4.9*7.6176

S = 37.33

Hence the window is 37.33m above the ground

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