Impulse

Force & Momentum Recall that Newton’s 2nd Law relates force (f), mass (m), and acceleration (a) in the following way:

Force & Momentum Also recall that acceleration is defined as: When substitute this into Newton’s 2nd Law we get

Force & Momentum Since (m∆v) is the change in momentum, we can now see that the force (F) is equal to the change in momentum divided by time (t). If we multiply both sides of the equation by the time (t), we get

Impulse Now we are left with the equation On the right, we have the change in momentum. On the left, we have the product of force (F) times time (t), which we will call the impulse.

Impulse We will represent the impulse acting on an object with the symbol (J). Impulse can be calculated using either of the two equations shown here: J = Ft J = mΔv If you are asked to calculate impulse itself, you must decide which equation is appropriate by looking at what information you are given.

Impulse Probably the most useful way to express this equation is Keep in mind whenever an object’s velocity or momentum is to the right, it is positive (+), and when they are to the left, they are negative (-).

Impulse Example 1: A 75 N force acts on an object for 3 s. Determine the impulse given to the object.

Impulse Example 2: A 60 kg object speeds up from 20 m/s to 35 m/s. How much impulse was necessary to cause this change in speed?

Impulse Example 3: How long must a 10 N force be exerted for in order to change the speed of a 20 kg object from 11 m/s to 18 m/s?

Impulse Example 3:

Impulse Example 4: An 18 kg object is initially moving at 25 m/s. If a 9 N force is applied to the object for 10 s, what will its final velocity be?

Impulse Example 4: