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anyanavicka [17]
3 years ago
6

A man stands on a platform that is rotating at 3.8 rpm; his arms are outstretched and he holds a brick in each hand. The rotatio

nal inertia of the system consisting of the man, bricks, and platform about the central axis of the platform is 4.65 kg-m². By moving the bricks the man decreases the rotational inertia of the system to 3.4 kg-m².
(a) what is the resulting angular speed of the platform and
(b) what is the ratio of the new kinetic energy of the system to the original kinetic energy?

Physics
2 answers:
Ierofanga [76]3 years ago
8 0

Answer:

a) 5.197rev/s

b) Kf/Ki =2.28

Explanation:

a) Angular momentum of the system L = Iw

ButLi=Lf

Kiwi =Ifwf

wf = (Ii/If)will = (4.65/3.4)×3.8=5.197rev/s

b)Kinetic energy KE= 0.5Iw^2

Ki = 0.5Iiwi^2

Kf=0.5Ifwf^2

Kf/Ki = Ifwf/Iiwi

Kf/Ki = (4.65/3.4))(5.197/3.8)

Kf/Ki = 1.22(1.368)^2

Kf/Ki = 2.28

kiruha [24]3 years ago
7 0

Answer:

A. 5.2 rpm.

B. Kf/Ki = 1.37.

Explanation:

Below is an attachment containing the solution.

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solniwko [45]

Answer:

32.3 m/s

Explanation:

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We start by analyzing the horizontal motion. The ball travels horizontally at constant speed of

v_x = 50 m/s

and it covers a distance of

d = 165 m

So, the total time of flight of the ball is

t=\frac{d}{v_x}=\frac{165}{50}=3.3 s

In order to find the vertical velocity of the ball, we have now to analyze its vertical motion.

The vertical motion is a free-fall motion, so the ball is falling at constant acceleration; therefore we can use the following suvat equation:

v_y = u_y +at

where

v_y is the vertical velocity at time t

u_y=0 is the initial vertical velocity

a=g=9.8 m/s^2 is the acceleration  of gravity (taking downward as positive direction)

Substituting t = 3.3 s (the time of flight), we find the final vertical velocity of the ball:

v=0 + (9.8)(3.3)=32.3 m/s

5 0
3 years ago
A sled with no initial velocity accelerates at a rate of 3.2 m/s2 down a hill. How long does it take the sled to go 15 m to the
grin007 [14]
S = ut + 1/2 at^2
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If a object is sliding across a surface, theoretically, it would not stop but because it is on a flat surface it would experience friction, this will disperse some of the kinetic energy that it has thus slowing the object down eventually, after some time, to a stop.

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8 0
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The load across a 12 v battery consists of a series combination of three resistors 45 ω, 55 ω, and 35 ω. what is the total resis
zubka84 [21]
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In this problem, we have three resistors, so the equivalent resistance of the load is the sum of the resistances of the three resistors:
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5 0
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