| Step | Derivation/Formula | Reasoning |
|---|---|---|
| 1 | \[\Delta x = \frac{1}{2} a t^2\] | Use constant–acceleration kinematics with initial velocity \(v_i = 0\). |
| 2 | \[a = \frac{2\Delta x}{t^2}\] | Algebraically isolate \(a\). |
| 3 | \[a = \frac{2(10)}{(4.5)^2} = 0.99\,\text{m/s}^2\] | Insert \(\Delta x = 10\,\text{m}\) and \(t = 4.5\,\text{s}\) to find \(a \approx 0.99\,\text{m/s}^2\). |
| 4 | \[F_{1x}=100\cos20^\circ,\;F_{2x}=-400\cos40^\circ,\;F_{3x}=500\cos10^\circ\] | Resolve each force into horizontal components; left is negative, right positive. |
| 5 | \[F_{1x}=93.97\,\text{N},\;F_{2x}=-306.6\,\text{N},\;F_{3x}=492.4\,\text{N}\] | Evaluate the trigonometric products. |
| 6 | \[F_{x,\text{applied}} = 279.8\,\text{N}\] | Sum \(F_{1x}+F_{2x}+F_{3x}\) to get the net applied horizontal force. |
| 7 | \[F_{1y}=+100\sin20^\circ,\;F_{2y}=-400\sin40^\circ,\;F_{3y}=-500\sin10^\circ\] | Resolve forces into vertical components; upward is positive. |
| 8 | \[F_{1y}=+34.2\,\text{N},\;F_{2y}=-257.1\,\text{N},\;F_{3y}=-86.8\,\text{N}\] | Compute the numeric values. |
| 9 | \[F_{y,\text{applied}} = -309.7\,\text{N}\] | Add the vertical components to find a downward net external load of \(309.7\,\text{N}\). |
| 10 | \[N = mg + 309.7\,\text{N}\] | Vertical equilibrium requires \(N + F_{1y} = mg + |F_{2y}| + |F_{3y}|\); simplify to this expression for the normal force. |
| 11 | \[f_k = \mu_k N = 0.2\,(mg + 309.7)\] | Kinetic friction opposes motion with magnitude \(\mu_k N\). |
| 12 | \[F_{\text{net}} = F_{x,\text{applied}} – f_k\] | Net horizontal force equals applied force minus friction (leftward). |
| 13 | \[ma = 279.8 – 0.2(mg + 309.7)\] | Apply Newton’s second law \(\sum F_x = ma\). |
| 14 | \[m(a + 1.96) = 217.8\] | Use \(g = 9.8\,\text{m/s}^2\) and simplify: \(0.2g = 1.96\,\text{N/kg}\). |
| 15 | \[m = \frac{217.8}{a + 1.96}\] | Isolate the unknown mass. |
| 16 | \[m = \frac{217.8}{0.99 + 1.96} = 73.9\,\text{kg}\] | Insert \(a \approx 0.99\,\text{m/s}^2\) to calculate \(m\). |
| 17 | \[\boxed{m \approx 7.4 \times 10^{1}\,\text{kg}}\] | Express the mass to two significant figures. |
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Ball A is dropped from the top of a cliff. At the same time, Ball B is thrown straight upward from the ground at \( 30 \) \( \text{m/s} \). The two balls pass each other after \( 2.0 \) \( \text{s} \).
Find the downward acceleration of an elevator, given that the ratio of a person’s stationary weight to their weight in the elevator is \(5:4\).
A \(5.5 \, \text{kg}\) block slides down a \(30^\circ\) incline that is \(2.2 \, \text{m}\) long. If \(\mu = 0.20\), what is the acceleration of the block?
Two balls have their centers \( 2.0 \) \( \text{m} \) apart. One ball has a mass of \( 8.0 \) \( \text{kg} \). The other has a mass of \( 6.0 \) \( \text{kg} \). What is the gravitational force between them?
An elevator starts at rest on the ground floor. It accelerates upward smoothly for \( 2 \) \( \text{s} \) until reaching a steady upward speed. It continues at that constant speed for \( 5 \) \( \text{s} \) before gently slowing to rest at the next floor in \( 3 \) \( \text{s} \). Draw the velocity vs. time graph.
A runner completes one full lap around a \( 400 \) \( \text{m} \) track in \( 100 \) \( \text{s} \). What is their average velocity?
A \( 1.5 \) \( \text{kg} \) block is pushed to the right with just enough force to get it to move. The block is pushed for five seconds with this constant force, then the force is released and the block slides to a stop. If the coefficient of kinetic friction is \( 0.300 \) and the coefficient of static friction is \( 0.400 \), calculate the amount of time that passes from when the force is applied to when the block stops.
Suppose you place a ball in the middle of a wagon, and then accelerate the wagon forward. Describe the motion of the ball relative to the ground. Describe its motion relative to the wagon.
A car travels \( 60 \) \( \text{km} \) at \( 30 \) \( \text{km/h} \), then \( 60 \) \( \text{km} \) at \( 60 \) \( \text{km/h} \). What is its average speed over the entire trip?
Which of the following graphs represent an object at rest?
\(74\,\text{kg}\)
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| Kinematics | Forces |
|---|---|
| \(\Delta x = v_i t + \frac{1}{2} at^2\) | \(F = ma\) |
| \(v = v_i + at\) | \(F_g = \frac{G m_1 m_2}{r^2}\) |
| \(v^2 = v_i^2 + 2a \Delta x\) | \(f = \mu N\) |
| \(\Delta x = \frac{v_i + v}{2} t\) | \(F_s =-kx\) |
| \(v^2 = v_f^2 \,-\, 2a \Delta x\) |
| Circular Motion | Energy |
|---|---|
| \(F_c = \frac{mv^2}{r}\) | \(KE = \frac{1}{2} mv^2\) |
| \(a_c = \frac{v^2}{r}\) | \(PE = mgh\) |
| \(T = 2\pi \sqrt{\frac{r}{g}}\) | \(KE_i + PE_i = KE_f + PE_f\) |
| \(W = Fd \cos\theta\) |
| Momentum | Torque and Rotations |
|---|---|
| \(p = mv\) | \(\tau = r \cdot F \cdot \sin(\theta)\) |
| \(J = \Delta p\) | \(I = \sum mr^2\) |
| \(p_i = p_f\) | \(L = I \cdot \omega\) |
| Simple Harmonic Motion | Fluids |
|---|---|
| \(F = -kx\) | \(P = \frac{F}{A}\) |
| \(T = 2\pi \sqrt{\frac{l}{g}}\) | \(P_{\text{total}} = P_{\text{atm}} + \rho gh\) |
| \(T = 2\pi \sqrt{\frac{m}{k}}\) | \(Q = Av\) |
| \(x(t) = A \cos(\omega t + \phi)\) | \(F_b = \rho V g\) |
| \(a = -\omega^2 x\) | \(A_1v_1 = A_2v_2\) |
| Constant | Description |
|---|---|
| [katex]g[/katex] | Acceleration due to gravity, typically [katex]9.8 , \text{m/s}^2[/katex] on Earth’s surface |
| [katex]G[/katex] | Universal Gravitational Constant, [katex]6.674 \times 10^{-11} , \text{N} \cdot \text{m}^2/\text{kg}^2[/katex] |
| [katex]\mu_k[/katex] and [katex]\mu_s[/katex] | Coefficients of kinetic ([katex]\mu_k[/katex]) and static ([katex]\mu_s[/katex]) friction, dimensionless. Static friction ([katex]\mu_s[/katex]) is usually greater than kinetic friction ([katex]\mu_k[/katex]) as it resists the start of motion. |
| [katex]k[/katex] | Spring constant, in [katex]\text{N/m}[/katex] |
| [katex] M_E = 5.972 \times 10^{24} , \text{kg} [/katex] | Mass of the Earth |
| [katex] M_M = 7.348 \times 10^{22} , \text{kg} [/katex] | Mass of the Moon |
| [katex] M_M = 1.989 \times 10^{30} , \text{kg} [/katex] | Mass of the Sun |
| Variable | SI Unit |
|---|---|
| [katex]s[/katex] (Displacement) | [katex]\text{meters (m)}[/katex] |
| [katex]v[/katex] (Velocity) | [katex]\text{meters per second (m/s)}[/katex] |
| [katex]a[/katex] (Acceleration) | [katex]\text{meters per second squared (m/s}^2\text{)}[/katex] |
| [katex]t[/katex] (Time) | [katex]\text{seconds (s)}[/katex] |
| [katex]m[/katex] (Mass) | [katex]\text{kilograms (kg)}[/katex] |
| Variable | Derived SI Unit |
|---|---|
| [katex]F[/katex] (Force) | [katex]\text{newtons (N)}[/katex] |
| [katex]E[/katex], [katex]PE[/katex], [katex]KE[/katex] (Energy, Potential Energy, Kinetic Energy) | [katex]\text{joules (J)}[/katex] |
| [katex]P[/katex] (Power) | [katex]\text{watts (W)}[/katex] |
| [katex]p[/katex] (Momentum) | [katex]\text{kilogram meters per second (kgm/s)}[/katex] |
| [katex]\omega[/katex] (Angular Velocity) | [katex]\text{radians per second (rad/s)}[/katex] |
| [katex]\tau[/katex] (Torque) | [katex]\text{newton meters (Nm)}[/katex] |
| [katex]I[/katex] (Moment of Inertia) | [katex]\text{kilogram meter squared (kgm}^2\text{)}[/katex] |
| [katex]f[/katex] (Frequency) | [katex]\text{hertz (Hz)}[/katex] |
Metric Prefixes
Example of using unit analysis: Convert 5 kilometers to millimeters.
Start with the given measurement: [katex]\text{5 km}[/katex]
Use the conversion factors for kilometers to meters and meters to millimeters: [katex]\text{5 km} \times \frac{10^3 \, \text{m}}{1 \, \text{km}} \times \frac{10^3 \, \text{mm}}{1 \, \text{m}}[/katex]
Perform the multiplication: [katex]\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}[/katex]
Simplify to get the final answer: [katex]\boxed{5 \times 10^6 \, \text{mm}}[/katex]
Prefix | Symbol | Power of Ten | Equivalent |
|---|---|---|---|
Pico- | p | [katex]10^{-12}[/katex] | |
Nano- | n | [katex]10^{-9}[/katex] | |
Micro- | µ | [katex]10^{-6}[/katex] | |
Milli- | m | [katex]10^{-3}[/katex] | |
Centi- | c | [katex]10^{-2}[/katex] | |
Deci- | d | [katex]10^{-1}[/katex] | |
(Base unit) | – | [katex]10^{0}[/katex] | |
Deca- or Deka- | da | [katex]10^{1}[/katex] | |
Hecto- | h | [katex]10^{2}[/katex] | |
Kilo- | k | [katex]10^{3}[/katex] | |
Mega- | M | [katex]10^{6}[/katex] | |
Giga- | G | [katex]10^{9}[/katex] | |
Tera- | T | [katex]10^{12}[/katex] |
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