| Derivation/Formula | Reasoning |
|---|---|
| \[\text{Forces:}\; N,\; mg,\; f_s\] | The diagram contains the normal reaction \(N\) acting perpendicular to the road surface, the weight \(mg\) acting vertically downward, and the static–friction force \(f_s\) acting up–slope while the rider is at rest on the hill. |
| \[mg\sin\theta,\; mg\cos\theta\] | The weight is resolved into components parallel (\(mg\sin\theta\), down–slope) and perpendicular (\(mg\cos\theta\)) to the incline of angle \(\theta=30^{\circ}\). |
| \[f_s\le \mu_sN\] | Static friction adjusts up to its maximum value \(\mu_sN\;(\mu_s=0.85)\) to keep the bicycle from sliding while the rider pauses. |
| Derivation/Formula | Reasoning |
|---|---|
| \[m=90\,\text{kg}+12\,\text{kg}=102\,\text{kg}\] | Total mass is the sum of rider and bicycle. |
| \[h=\Delta x_1\sin\theta=9\,(0.5)=4.5\,\text{m}\] | The vertical drop after rolling \(\Delta x_1=9\,\text{m}\) down a \(30^{\circ}\) incline is \(h=\Delta x_1\sin\theta\). |
| \[v_i=\sqrt{2gh}=\sqrt{2(9.8)(4.5)}\] | Conservation of energy (no non-conservative work before braking) gives the speed \(v_i\) at the instant the wheels lock. |
| \[v_i\approx9.4\,\text{m\,s}^{-1}\] | Numeric evaluation of the previous expression. |
| \[F_f=\mu_kN=\mu_kmg\cos\theta\] | Once the wheels are locked, kinetic friction of magnitude \(F_f\) opposes the motion (\(\mu_k=0.7\)). |
| \[F_f=0.7(102)(9.8)(0.866)=6.06\times10^{2}\,\text{N}\] | Calculating the friction force with \(\cos30^{\circ}=0.866\). |
| \[\Delta x_2=\frac{\tfrac12v_i^{2}}{g(\mu_k\cos\theta-\sin\theta)}\] | Work–energy: net work \(mg\sin\theta\Delta x_2-F_f\Delta x_2=-\tfrac12mv_i^{2}\). Solving for stopping distance \(\Delta x_2\). |
| \[\Delta x_2\approx42.5\,\text{m}\] | Numeric substitution using \(\mu_k\cos\theta-\sin\theta\approx0.106\). |
| \[W_f=-F_f\Delta x_2\] | Work done by friction is negative because it opposes the displacement down the slope. |
| \[\boxed{W_f\approx-2.6\times10^{4}\,\text{J}}\] | Final numeric value of energy removed by kinetic friction to bring the bicycle to rest. |
| Derivation/Formula | Reasoning |
|---|---|
| \[F_{\text{up}}=mg\sin\theta+f\] | When climbing at constant speed the cyclist’s legs must generate an up-slope force equal to gravity’s component \(mg\sin\theta\) plus rolling/drag/friction forces \(f\). |
| \[F_{\text{down}}=mg\sin\theta-f\] | During descent gravity supplies \(mg\sin\theta\); only a portion is cancelled by friction or air drag, so the net driving force is \(mg\sin\theta-f\) acting without muscular effort. |
| \[F_{\text{up}}>F_{\text{down}}\] | Because \(f>0\), the force required from the cyclist on the climb is strictly larger than the net force aiding motion downhill, making ascent harder than descent. |
| \[W_{\text{climb}}=mg\,h\;>\;0,\quad W_{\text{down}}=-mg\,h\] | Energy must be supplied to increase gravitational potential when going up (positive work), whereas gravity returns that energy on the way down (negative work done by the rider), confirming the greater effort needed to ascend. |
A Major Upgrade To Phy Is Coming Soon — Stay Tuned
We'll help clarify entire units in one hour or less — guaranteed.
A self paced course with videos, problems sets, and everything you need to get a 5. Trusted by over 15k students and over 200 schools.
Two identical arrows, one with \( 2 \) times the speed of the other, are fired into a bale of hay. Assuming the hay exerts a constant “frictional” force on the arrows, the faster arrow will penetrate how much farther than the slower arrow?
A box having a mass of \( 1.5 \) \( \text{kg} \) is accelerated across a table at \( 1.5 \) \( \text{m/s}^2 \). The coefficient of kinetic friction on the box is \( 0.3 \).
An object is projected vertically upward from ground level. It rises to a maximum height \( H \). If air resistance is negligible, which of the following must be true for the object when it is at a height \( H/2 \) ?
A pendulum bob of mass m on a cord of length L is pulled sideways until the cord makes an angle \( \theta \) with the vertical. The change in potential energy of the bob during the displacement is:
An object of mass 2 kg is thrown vertically downwards with an initial kinetic energy of 100 J. What is the distance fallen by the object at the instant when its kinetic energy has doubled?
In the figure above, the marble rolls down the track and around a loop-the-loop of radius \( R \). The marble has mass \( m \) and radius \( r \). What minimum height \( h_{min} \) must the track have for the marble to make it around the loop-the-loop without falling off? Express your answer in terms of the variables \( R \) and \( r \).
A baseball is thrown vertically into the air with a velocity \( v \), and reaches a maximum height \( h \). At what height was the baseball moving with one-half its original velocity? Assume air resistance is negligible.
A mechanic pushes a \(2500 \, \text{kg}\) car from rest to a final speed \(v\) by doing \(5.0 \times 10^3 \, \text{J}\) of work on the car. Frictional effect between the car and the ground are negligible. What is the final speed of the car?
The launching mechanism of a toy gun consists of a spring with an unknown spring constant, \( k \). When the spring is compressed \( 0.120 \, \text{m} \) vertically, a \( 35.0 \, \text{g} \) projectile is able to be fired to a maximum height of \( 25 \, \text{m} \) above the position of the projectile when the spring is compressed. Assume that the barrel of the gun is frictionless.
A linear spring of negligible mass requires a force of \( 18.0 \, \text{N} \) to cause its length to increase by \( 1.0 \, \text{cm} \). A sphere of mass \( 75.0 \, \text{g} \) is then attached to one end of the spring. The distance between the center of the sphere \( M \) and the other end \( P \) of the un-stretched spring is \( 25.0 \, \text{cm} \). Then the sphere begins rotating at constant speed in a horizontal circle around the center \( P \). The distance \( P \) and \( M \) increases to \( 26.5 \, \text{cm} \).
By continuing you (1) agree to our Terms of Use and Terms of Sale and (2) consent to sharing your IP and browser information used by this site’s security protocols as outlined in our Privacy Policy.
| 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] |
One price to unlock most advanced version of Phy across all our tools.
per month
Billed Monthly. Cancel Anytime.
Try our free calculator to see what you need to get a 5 on the 2026 AP Physics 1 exam.
Understand you mistakes quicker.
Phy automatically provides feedback so you can improve your responses.
10 Free Credits To Get You Started
By continuing you agree to nerd-notes.com Terms of Service, Privacy Policy, and our usage of user data.
Feeling uneasy about your next physics test? We'll boost your grade in 3 lessons or less—guaranteed
