Impulse and Impulsive Force

Card 1: What is Impulse?

Impulse

Impulse is defined as the product of the force (F) acting on an object and the time of action (t).

Impulse exerted on an object is equal to the momentum change of the object.

Impulse is a vector quantity.

Card 2: Formula of Impulse

Formula of impulse

Impulse is the product of force and time.

Impulse = F × t

Impulse = momentum change

Impulse = mv - mu

Example 1
A car of mass 600kg is moving with velocity of 30m/s. A net force of 200N is applied on the car for 15s. Find the impulse exerted on the car and hence determine the final velocity of the car.

Answer:

Impulse = F × t = (200) × (15) = 300oNs

Impulse = mv - mu
(3000) = 600v - 600(30)
600v = 3000 + 18000
v = 21000/600 = 35 m/s

[500,000N]

 

Card 3: What is impulsive force?

Impulsive Force

Impulsive force is defined as the rate of change of momentum in a reaction.

It is a force which acts on an object for a very short interval during a collision or explosion.

Example 2
A car of mass 1000kg is traveling with a velocity of 25 m/s. The car hits a street lamp and is stopped in0.05 seconds. What is the impulsive force acting on the car during the crash?

Answer:

            \begin{gathered}
  {\text{Impulsive Force,}} \hfill \\
  F = \frac{{m(v - u)}}
{t} \hfill \\
  F = \frac{{1000(0 - 25)}}
{{0.05}} \hfill \\
  F = -500,000N \hfill \\ 
\end{gathered}
            

 

Card 4: Effects of Impulse vs Force

Effects of impulse vs Force

A force determines the acceleration (rate of velocity change) of an object. A greater force produces a higher acceleration.

An impulse determines the velocity change of an object. A greater impulse yield a higher velocity change.

Card 5: Examples Involving Impulsive Force

Examples Involving Impulsive Force

  • Playing football
  • Playing badminton
  • Playing tennis
  • Playing golf
  • Playing baseball
Card 6: Effect of time on impulsive force 1 - Long Jump

Long Jump

long jump

  • The long jump pit is filled with sand to increase the reaction time when atlete land on it.
  • This is to reduce the impulsive force acts on the leg of the atlete because impulsive force is inversely proportional to the reaction time.
Card 7: Effect of time on impulsive force 1 - High Jump

High Jump


(This image is licenced under the GNU Free Document Licence. The original file is from the Wikipedia.org.)

  • During a high jump, a high jumper will land on a thick, soft mattress after the jump.
  • This is to increase the reaction time and hence reduces the impulsive force acting on the high jumper.
Card 8: Effect of time on impulsive force 1 - Jumping

Jumping

A jumper bends his/her leg during landing. This is to increase the reaction time and hence reduce the impact of impulsive force acting on the leg of the jumper.

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Card 10: Empty Card

 

 

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