The half-life of a radioactive substance is 10 days. After 30 days, the fraction decayed is MCQ with Answer and Explanation

Explanation:
F = G m1 m2 / r² => G = F r² / (m1 m2) => [MLT⁻²][L²]/[M²] = [M⁻¹L³T⁻²].

Explanation:
Fuse uses heating effect (Joule heating I²R). When current exceeds limit, fuse wire melts due to heat, breaking circuit. Motor uses magnetic effect, generator uses electromagnetic induction, galvanometer detects current. Iron box, heater also use heating effect.

Explanation:
When the stone is moving in a circle, its velocity vector is always tangential to the circle. The string provides the necessary centripetal force directed towards the center. When the string breaks, this inward force ceases to exist. Due to inertia of direction (Newton's First Law), the stone continues to move along the tangent at the point where the string broke.