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ICSE Class 9 Physics Question 1 of 20

Laws of Motion — Question 5

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Question

Question 5

The correct form of Newton's second law is —

  1. F = ΔpΔt\dfrac{Δ\text p}{Δ\text t}

  2. F = m ΔvΔt\dfrac{Δ\text v}{Δ\text t}

  3. F = v ΔmΔt\dfrac{Δ\text m}{Δ\text t}

  4. F = mv

Answer

F = ΔpΔt\dfrac{Δ\text p}{Δ\text t}

Reason — As we know,

Force = Rate of change of momentum

F = ΔpΔt\dfrac{Δ\text p}{Δ\text t}

= Δ(mv)Δt\dfrac{Δ\text {(mv)}}{Δ\text t}

= m(Δv)Δt\dfrac{\text m(Δ\text v)}{Δ\text t}

= ma

Thus, Newton’s second law will be F = ΔpΔt\dfrac{Δ\text p}{Δ\text t}