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Vikki [24]
2 years ago
14

You stand on a bridge above a river and drop a rock into the water below from a height of 25 m. (Assume no air resistance)

Physics
1 answer:
Ilia_Sergeevich [38]2 years ago
5 0

PART a)

here when stone is dropped there is only gravitational force on it

so its acceleration is only due to gravity

so we will have

a = g = 9.8 m/s^2

Part b)

Now from kinematics equation we will have

y = v_i t + \frac{1}{2} at^2

now we have

y = 25 m

so from above equation

25 = 0 + \frac{1}{2}(9.8 )t^2

t = 2.26 s

Part c)

If we throw the rock horizontally by speed 20 m/s

then in this case there is no change in the vertical velocity

so it will take same time to reach the water surface as it took initially

So t = 2.26 s

Part D)

Initial speed = 20 m/s

angle of projection = 65 degree

now we have

v_x = vcos\theta

v_x  = 20 cos65 = 8.45 m/s

v_y = vsin\theta

v_y = 20 sin65 = 18.13 m/s

PART E)

when stone will reach to maximum height then we know that its final speed in y direction becomes zero

so here we can use kinematics in Y direction

v_f - v_y = at

0 - 18.13 = (-9.8) t

t = 1.85 s

so it will take 1.85 s to reach the top

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A fireman is sliding down a fire pole. As he speeds up, he tightens his grip on the pole, thus increasing the vertical frictiona
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Answer:

The fireman will continue to descend, but with a constant speed.

Explanation:

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We need to understand the difference between static friction and kinetic friction.

Static friction occurs in objects that are stationary, while kinetic friction occurs in objects that are already in motion.  

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8 0
3 years ago
We wrap a light, nonstretching cable around a 8.00 kg solid cylinder with diameter of 30.0 cm. The cylinder rotates with negligi
antoniya [11.8K]

Answer:

h = 16.67m

Explanation:

If the kinetic energy of the cylinder is 510J:

Kc=510=1/2*Ic*\omega c^2

\omega c=\sqrt{510*2/Ic}

Where the inertia is given by:

Ic=1/2*m_c*R_c^2=1/2*(8)*(0.15)^2=0.0225kg.m^2

Replacing this value:

\omega c=106.46rad/s

Speed of the block will therefore be:

V_b=\omega_c*R_c=106.46*0.15=15.969m/s

By conservation of energy:

Eo = Ef

Eo = 0

Ef = 510+1/2*m_b*V_b^2-m_b*g*h

So,

0 = 510+1/2*m_b*V_b^2-m_b*g*h

Solving for h we get:

h=16.67m

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Answer:When white light strikes an object, each individual frequency of light is transmitted, reflected, or absorbed, depending on the properties of the surface molecules. If all frequencies are absorbed by the object, then it appears black. If all frequencies are reflected, then it appears white.

Explanation:

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A certain 48 V electric forklift can lift up to 7000 lb at a
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Answer:

256.25 A

Explanation:

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