As you know, momentum is the product of the mass of an object and its velocity. It could be expressed in any units of mass or velocity but as a standard it is expressed in Kg m/s:


A body with a fixed mass moving at a constant velocity will have a fixed momentum, but if that body has an external force applied to it (a non-zero resultant force) then its momentum will change.


Any change in velocity, whether it is an increase or decrease represents an acceleration which is calculated by dividing the change in velocity by the time taken:


From Newton's Second Law, Force applied on an object is the product of the object's mass and its acceleration, therefore if we combine the equations, we can represent the effect of an applied force in terms of the change in momentum produced:

Q. An object with a mass of 175g, travelling at 35 m/s is subjected to a non zero resultant force, over a period of 7 seconds which increases its velocity to 72 m/s. Calculate the magnitude of the non zero resultant force.


A. 



Remember that "Delta V" is the change in velocity. Sometimes the question will give you an initial velocity, and the final velocity. The change is obviously the difference between the two, but in other cases you may have an implied initial velocity of zero, such as in the case of a golf ball being struck by a golf club or a bullet being fired out of a gun.


Where v is the final velocity, u is the initial velocity.



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