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Step Calculation/Analysis Description
1 T_{\text{max, stationary}} = m_{\text{operator}} \times g Maximum stationary tension with the operator’s weight. m_{\text{operator}} = 90 , \text{kg}, g = 9.81 , \text{m/s}^2.
2 v = \frac{2\pi \times L}{T} Rotation speed calculation. L = 10 , \text{m}, T = 3 , \text{s}.
3.1 T_{\text{horizontal}} = F_{\text{centripetal}} Horizontal component of tension equals centripetal force.
3.2 F_{\text{centripetal}} = \frac{m_{\text{child}} \times v^2}{r} Centripetal force formula. m_{\text{child}} = 25 , \text{kg}.
3.3 r = L \sin(\theta) Effective radius related to the angle .
3.4 F_{\text{centripetal}} = \frac{m_{\text{child}} \times v^2}{L \sin(\theta)} Substitute r in centripetal force formula.
3.5 T_{\text{vertical}} = m_{\text{child}} \times g Vertical component of tension equals child’s weight.
3.6 \tan(\theta) = \frac{T_{\text{horizontal}}}{T_{\text{vertical}}} Relation between tension components.
3.7 \tan(\theta) = \frac{m_{\text{child}} \times v^2 / (L \sin(\theta))}{m_{\text{child}} \times g} Substitute velocity and radius in the tangent formula.
3.8 cos\theta = \frac{9}{4\pi^2} Final, simplified equation
3.9 \theta = \approx 76.8 Approximate value of the angle to the vertical of any rider (angle does not depend of mass).
4 T_{\text{ride}}cos\theta = mg Solve for tension to get a total tension of ~ 1290 N for when the child sits in the seat. Remember the to add the mass of the seat to the child.
5 Safety Assessment Tension in the chain is greater while child is rotating than when operator is sitting in it stationary, indicating the chain might break when the child is rotating in it.

M

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No it is not safe for the child. Based on the rotational speed, the child would be raised to an angle of ~77° from the initial vertical position. At this point the tension in the chain (~1290 N), while rotating, is considerable greater than the maximum force of tension (~920 N) the chain can with stand.

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##### Made By Nerd-Notes.com
KinematicsForces
\Delta x = v_i t + \frac{1}{2} at^2F = ma
v = v_i + atF_g = \frac{G m_1m_2}{r^2}
a = \frac{\Delta v}{\Delta t}f = \mu N
R = \frac{v_i^2 \sin(2\theta)}{g}
Circular MotionEnergy
F_c = \frac{mv^2}{r}KE = \frac{1}{2} mv^2
a_c = \frac{v^2}{r}PE = mgh
KE_i + PE_i = KE_f + PE_f
MomentumTorque and Rotations
p = m v\tau = r \cdot F \cdot \sin(\theta)
J = \Delta pI = \sum mr^2
p_i = p_fL = I \cdot \omega
Simple Harmonic Motion
F = -k x
T = 2\pi \sqrt{\frac{l}{g}}
T = 2\pi \sqrt{\frac{m}{k}}
ConstantDescription
gAcceleration due to gravity, typically 9.8 , \text{m/s}^2 on Earth’s surface
GUniversal Gravitational Constant, 6.674 \times 10^{-11} , \text{N} \cdot \text{m}^2/\text{kg}^2
\mu_k and \mu_sCoefficients of kinetic (\mu_k) and static (\mu_s) friction, dimensionless. Static friction (\mu_s) is usually greater than kinetic friction (\mu_k) as it resists the start of motion.
kSpring constant, in \text{N/m}
M_E = 5.972 \times 10^{24} , \text{kg} Mass of the Earth
M_M = 7.348 \times 10^{22} , \text{kg} Mass of the Moon
M_M = 1.989 \times 10^{30} , \text{kg} Mass of the Sun
VariableSI Unit
s (Displacement)\text{meters (m)}
v (Velocity)\text{meters per second (m/s)}
a (Acceleration)\text{meters per second squared (m/s}^2\text{)}
t (Time)\text{seconds (s)}
m (Mass)\text{kilograms (kg)}
VariableDerived SI Unit
F (Force)\text{newtons (N)}
E, PE, KE (Energy, Potential Energy, Kinetic Energy)\text{joules (J)}
P (Power)\text{watts (W)}
p (Momentum)\text{kilogram meters per second (kgm/s)}
\tau (Torque)\text{newton meters (Nm)}
I (Moment of Inertia)\text{kilogram meter squared (kgm}^2\text{)}
f (Frequency)\text{hertz (Hz)}

General Metric Conversion Chart

Example of using unit analysis: Convert 5 kilometers to millimeters.

1. Start with the given measurement: \text{5 km}

2. Use the conversion factors for kilometers to meters and meters to millimeters: \text{5 km} \times \frac{10^3 \, \text{m}}{1 \, \text{km}} \times \frac{10^3 \, \text{mm}}{1 \, \text{m}}

3. Perform the multiplication: \text{5 km} \times \frac{10^3 \, \text{m}}{1 \, \text{km}} \times \frac{10^3 \, \text{mm}}{1 \, \text{m}} = 5 \times 10^3 \times 10^3 \, \text{mm}

4. Simplify to get the final answer: \boxed{5 \times 10^6 \, \text{mm}}

Prefix

Symbol

Power of Ten

Equivalent

Pico-

p

10^{-12}

Nano-

n

10^{-9}

Micro-

µ

10^{-6}

Milli-

m

10^{-3}

Centi-

c

10^{-2}

Deci-

d

10^{-1}

(Base unit)

10^{0}

Deca- or Deka-

da

10^{1}

Hecto-

h

10^{2}

Kilo-

k

10^{3}

Mega-

M

10^{6}

Giga-

G

10^{9}

Tera-

T

10^{12}

1. Some answers may be slightly off by 1% depending on rounding, etc.
2. Answers will use different values of gravity. Some answers use 9.81 m/s2, and other 10 m/s2 for calculations.
3. Variables are sometimes written differently from class to class. For example, sometime initial velocity v_i is written as u ; sometimes \Delta x is written as s .
4. Bookmark questions that you can’t solve so you can come back to them later.
5. Always get help if you can’t figure out a problem. The sooner you can get it cleared up the better chances of you not getting it wrong on a test!

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