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According to Coulomb's Law, the force $F$ between two charges $q_1$ and $q_2$ separated by distance $r$ is:
$F = \frac{1}{4\pi\epsilon_0} \frac{q_1 q_2}{r^2}$
Rearranging for permittivity:
$\epsilon_0 = \frac{q^2}{4\pi F r^2}$
Dimensional analysis:
- Charge $[q] = [AT]$
- Force $[F] = [MLT^{-2}]$
- Distance $[r] = [L]$
$[\epsilon_0] = \frac{[A^2 T^2]}{[M L T^{-2}] [L^2]} = [M^{-1} L^{-3} T^4 A^2]$
A suspense account was opened after a trial balance failed to agree. Errors found:
- Sales invoice for $1,240 completely omitted.
- Purchases entered as $85,600 instead of $87,580.
- Rent paid $2,600 posted as $6,200 in rent account.
What was the original balance on the suspense account?
Option A ($1,620 credit) is correct.
Only one-sided errors affect the suspense account:
- Error 1 (complete omission): Does NOT affect suspense.
- Error 2: Purchases understated by $1,980 → Debit Purchases, Credit Suspense $1,980.
- Error 3: Rent overposted by $3,600 → Debit Suspense, Credit Rent $3,600.
Net: Dr $3,600 − Cr $1,980 = Dr $1,620 needed → original balance was $1,620 credit.
Generally increases left to right, but N (half-filled 2p³) has unexpectedly higher IE₁ than O (2p⁴, one electron paired → easier to remove). So:
Correct order: B < C < O < N (N before O is reversed)
The statement B < C < N < O suggests O has higher IE₁ than N — this is wrong. Option (2) is incorrect.
1. Find Cube Side ($a$): The body diagonal of the cube equals the diameter of the sphere. $\sqrt{3}a = 2R \implies a = \frac{2R}{\sqrt{3}}$.
2. Find Cube Mass ($m$): Density $\rho = \frac{M}{\frac{4}{3}\pi R^3}$. Mass of cube $m = \rho \times a^3 = \left(\frac{3M}{4\pi R^3}\right) \times \left(\frac{8R^3}{3\sqrt{3}}\right) = \frac{2M}{\pi \sqrt{3}}$.
3. Moment of Inertia ($I$): For a cube about the center-face axis, $I = \frac{ma^2}{6}$.
$I = \frac{1}{6} \left( \frac{2M}{\pi \sqrt{3}} \right) \left( \frac{4R^2}{3} \right) = \frac{8MR^2}{18\pi \sqrt{3}} = \frac{4MR^2}{9\sqrt{3}\pi}$.
Sales revenue $500,000; Total costs $400,000; Fixed costs $120,000. What was the total contribution?
Option B ($220,000) is correct.
Variable costs = $400,000 − $120,000 = $280,000
Contribution = $500,000 − $280,000 = $220,000
(Note: Profit = $220,000 − $120,000 = $100,000 — that is Option A, not the same as contribution.)
The three levels of prevention are:
| Level | Target | Examples |
|---|---|---|
| Primary | Healthy population — prevent disease onset | Immunization, health education, clean water, nutrition |
| Secondary | Early detection and treatment | Screening, early diagnosis, prompt treatment |
| Tertiary | Reduce disability, restore function | Rehabilitation, chronic disease management |
Immunization is a classic example of primary prevention as it prevents disease before it occurs.
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