Impulse

Definition

• Impulse is defined as the product of the average force (F) and the time of contact (Δt) during a collision:

Mathematical Expression

• Impulse (J) = F × Δt

Units

• Impulse is measured in Newton-seconds (Ns), which is equivalent to kilogram meters per second (kg m/s).

Relation to Momentum

• Impulse is closely related to momentum and can be expressed as the change in momentum:
• Change in momentum (Δp) = Impulse (J)
• Δp = F × Δt

Newton's Second Law and Impulse

• Newton's Second Law states that the force acting on an object is equal to the rate of change of its momentum:
• F = Δp/Δt

Impulse-Momentum Theorem

• The impulse-momentum theorem states that the change in momentum of an object is equal to the impulse applied to it:
• Δp = J
• This theorem is a useful tool in analysing collisions and the effects of forces on objects.

Example

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Impulse

Calculating Impulse and Average Force

• Using the equation for change in momentum:
  • Δp = m × (v - u)
  • Δp = 0.025 kg × (8.4 m/s - 3.2 m/s)
  • Δp = 0.025 kg × 5.2 m/s
  • Δp = 0.13 kg m/s
• Impulse (J) is equal to the change in momentum:
  • J = Δp
  • J = 0.13 kg m/s
• To calculate the average force (F), we use the formula for impulse:
  • J = F × Δt
  • 0.13 kg m/s = F × 4 × 10^(-3) s
• Solving for F:
  • F = (0.13 kg m/s) / (4 × 10^(-3) s)
  • F = 32.5 N

Interpretation

• The average force applied by the squash racquet to change the squash ball's momentum is 32.5 N.