Explanation

Use Newton’s 2nd law: F = m Δv/Δt

Δv = 10 – 20 = –10 m/s, m = 150 kg, Δt = 3 s

F = 150 × (–10 / 3) ≈ –500 N

Magnitude of braking force = 500 N.

Explanation

In a displacement-time graph, slope = velocity.

Straight line → slope constant → velocity remains constant.

Explanation

Use the formula: cosθ = (A · B) / (|A||B|)

A · B = (2)(-6) + (3)(4) = -12 + 12 = 0

|A| = √(2² + 3²) = √13, |B| = √((-6)² + 4²) = √52

cosθ = 0 / (√13 × √52) = 0 → θ = 90°

Explanation

For opposite charges, electric fields point toward negative and away from positive.

Between them, the fields add up, so no point exists where the net field is zero.

Explanation

Newton used isothermal process (constant temperature) to calculate sound speed.

Actual sound propagation is adiabatic, so his formula underestimated the speed.

Explanation

At terminal velocity, gravitational force is balanced by viscous drag.

Net force = 0 → acceleration becomes zero, motion continues at constant speed.

Explanation

In a transformer, Vₛ/Vₚ = Nₛ/Nₚ and Iₛ/Iₚ = Nₚ/Nₛ.

Step-up voltage by 10 → secondary current decreases by 10 → Iₛ = Iₚ / 10.

Explanation

Work done: W = F × d × cosθ

If force and displacement are opposite → θ = 180° → cos180° = -1 → work is negative.

Explanation

Linear displacement in circular motion: s = r × θ

If θ is constant, reducing r → s decreases.

Explanation

Work done by force: W = F × Δd

Power (rate of doing work) = P = W / Δt = F × Δd / Δt