let the length of the beam be "L"
from the diagram
AD = length of beam = L
AC = CD = AD/2 = L/2
BC = AC - AB = (L/2) - 1.10
BD = AD - AB = L - 1.10
m = mass of beam = 20 kg
m₁ = mass of child on left end = 30 kg
m₂ = mass of child on right end = 40 kg
using equilibrium of torque about B
(m₁ g) (AB) = (mg) (BC) + (m₂ g) (BD)
30 (1.10) = (20) ((L/2) - 1.10) + (40) (L - 1.10)
L = 1.98 m
Answer:

Explanation:
we know angular velocity in terms of moment of inertia and angular speed
ω .... (1)
moment of inertia of rod rotating about its center of length b
........ .(2)
using v = ωr
where w is angular velocity
and r is radius of rod which is equal to b
so we get 2v = ωb
ω = 2v/b ................. (3)
here velocity is two time because two opposite ends are moving opposite with a velocity v so net velocity will be 2v
put second and third equation in ist equation
×
so final answer will be 
Answer:
The speed in the first point is: 4.98m/s
The acceleration is: 1.67m/s^2
The prior distance from the first point is: 7.42m
Explanation:
For part a and b:
We have a system with two equations and two variables.
We have these data:
X = distance = 60m
t = time = 6.0s
Sf = Final speed = 15m/s
And We need to find:
So = Inicial speed
a = aceleration
We are going to use these equation:


We are going to put our data:


With these equation, you can decide a method for solve. In this case, We are going to use an egualiazation method.



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If we analyze the situation, we need to have an aceleretarion greater than cero. We are going to choose a = 1.67m/s^2
After, we are going to determine the speed in the first point:




For part c:
We are going to use:




Answer:
Force applied to smaller cross section is
= 82.63 N
Explanation:
As we know

where
signifies the weight of the two chair in a hydraulic-lift system
And
signifies the area of the two respective chairs in a hydraulic-lift system
Given -
N
Square centimeter
Square centimeter
Substituting the given values in above equation, we get -

Force applied to smaller cross section is
= 82.63 N
Answer:
a) Earth
b) Mercury
c) Neptune
Explanation:
All the planets move around the sun in eastward direction, but few planet have retrograde rotation i.e in westward direction. Retrograde motion is just an apparent change in the movement of planet which means it only seems as if the planet are rotating in opposite direction. Retrograde movement of planet like Saturn, Jupiter and mars is not real. Hence, if a person lives on Saturn, then following planets will exhibit retrograde motion
a) Earth
b) Mercury
c) Neptune