Impulse vs Impact
The words impact and impulse are freely used in our daily lives. Lawyers try to minimize the impact of the crime committed by their clients by saying that it was on an impulsive action that was on the spur of the moment and not really intentional. We get to know about the impact great people had on the minds of successful people of today in their autobiographies and the sudden feeling or an impulse people have to indulge in an act that was totally predetermined. But is there only this much between impact and impulse? These are terms widely used in physics in the study of motion (mechanics). There are many differences in the two concepts that will be harped upon in this article.
When a force is applied to a body, it changes its momentum. The relation between the force and the change in velocity of a body is given by Newton’s 2nd law of motion in the following equation
F = m X a = ma
Where F is the force applied, m is the mass of the body and ‘a’ is its acceleration. Now, we know that acceleration is rate of change of velocity
Hence F = m X (v1 – v2)/t
Or, F X t = m X (v1 – v2)
i.e, Ft = m(v1 – v2)
But the product of mass and its velocity is its momentum
Thus F x t = change in momentum
This implies that change in momentum of a body is a product of the force applied on it for some duration.
This also means that same change in momentum can be induced in a body with a large force operating over a small time period and a small force operating over a long period of time.
Impact is another important concept in the study of collisions of moving bodies and their results. Impact is the sudden force felt by two bodies when they collide. The impact or the force felt by bodies is in direct proportion to the amount of force and the time period for which collision takes place. Impact is dependent upon the relative velocities of the two bodies that collide. In the game of cricket, more force is required on the part of the batsman to send the bowl bowled by a fast bowler back past the bowler than guiding the ball past the wicketkeeper. This is because he utilizes the velocity of the fast moving ball and merely guides it over the head of the wicketkeeper than when he forces it back past the bowler.
The study of impact is very helpful in designing automobiles as designers can minimize the effect of the impact during collision by increasing the impact resistance of the automobile. This is sought to be achieved by making front of the car to absorb maximum impact of the kinetic energy of the vehicle coming from the opposite direction allowing only a small part of this energy to reach the driver.
What is the difference between Impulse and Impact?
• Impact force and impulse force are effects of force understood in different respects
• While impulse is understood in terms of change in momentum of a body and is a function of force applied and the time period for which it is applied, impact force is the force applied over a very short period of time.
• Impact has the same unit as force while impulse is expressed in terms of units of momentum which are kg m/s
• Impulse is an integral of force over time which is why it has units different from that of force.