JAMB Physics Past Questions & Answers - Page 148

- Alpha radiation consists of helium- He$^{4}_{2}$

2 Alpha decay --> 2  X  He$^{4}_{2}$ = Element$^{8}_{4}$ 

- Beta particles are high energy electrons-  e$^{0}_{-1}$

3 Beta particles --> 3  X  e$^{0}_{-1}$ = Element$^{0}_{-3}$

- Gamma rays are waves of electromagnetic energy, or photons.

the mass and atomic number of the resulting element = U$^{235}_{92}$ - Elements( $^{8}_{4}$ +  $^{0}_{-3}$ )

--> Element$^{227}_{91}$ 

No explanation has been provided for this answer.

Neutral Equilibrium: If the body neither returns to its original position nor increases its displacement further, it will simply adopt its new position.

Examples of neutral equilibrium

• Ball moving on the ground.
• Motion of sphere.
• A roller.
• A pencil lying horizontally.
• An egg lying horizontally on a flat surface.

Comparing $y = 10 \text{Sin} (1000\pi t - \frac{\pi x}{34})$ with y = A sin (ωt - ϕ)

where ϕ = $\frac{2\pi x}{λ}$

comparing:  $\frac{2\pi x}{λ}$ = $\frac{\pi x}{34}$

λ = 34 $\times$ 2 = 68

: ϕ =  $\frac{2\pi x}{λ}$ =  $\frac{2\pi \times 153}{68}$

ϕ = 4.5$\pi$ rad = 810° or 90°

since sin 810° or 90° = 1

80 days = 4 half lives (i.e 4 x 20dqs = 80dq)

But the fraction always left by any radioactive material after 4 half lives is

$\left ( \frac{1}{2} \right)^4 = \frac{1}{16}$