Physics Principles Flashcards

A block of mass 5 kg slides down a frictionless incline angled at 30°. What is its acceleration? (g = 10 m/s²)

Answer: 5 m/s²

Acceleration along the incline = g sin 30° = 10 × 0.5 = 5 m/s².

Two resistors of 6 Ω and 3 Ω are connected in parallel. What is their combined resistance?

Answer: 2 Ω

1/R = 1/6 + 1/3 = 1/6 + 2/6 = 3/6 → R = 2 Ω.

Which of the following quantities is conserved in all types of collisions?

Answer: Momentum only

Momentum is always conserved in collisions; kinetic energy is conserved only in perfectly elastic collisions.

A glass lens immersed in water has a lower refracting power than in air. This is because:

Answer: The refractive index difference between glass and water is smaller than between glass and air

Lens power depends on the relative refractive index (n_glass/n_medium); since n_water ≈ 1.33, the contrast with glass is less than in air (n = 1.0).

What happens to the period of a simple pendulum if its length is quadrupled?

Answer: It doubles

T = 2π√(L/g); quadrupling L increases √L by a factor of 2, so the period doubles.

A photon has energy 3.0 × 10⁻¹⁹ J. Given h = 6.63 × 10⁻³⁴ J·s and c = 3 × 10⁸ m/s, what is its wavelength?

Answer: 663 nm

λ = hc/E = (6.63×10⁻³⁴ × 3×10⁸) / (3×10⁻¹⁹) ≈ 663 nm (red light).

An object floats in water with 40% of its volume submerged. What is the object's density? (ρ_water = 1000 kg/m³)

Answer: 400 kg/m³

By Archimedes' principle, ρ_object/ρ_water = fraction submerged → ρ_object = 0.40 × 1000 = 400 kg/m³.