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A 2-kg object accelerates as a net external force is applied to it. During the 5-second interval that the force is applied, the object's velocity changes from 3 m/s East to 7 m/s West. Several students discussing the impulse on this object state the following:

Student #1: "The impulse is equal to the change in momentum, which is (2 kg)(3 m/s + 7 m/s) = 20 kg m/s."

Student #2: "But the change in velocity is 4 m/s. We multiply by the mass to get the change in momentum, and also the impulse, which is 8 kg m/s."

Student #3: "The change in momentum of this object during these 5 seconds was 8 kg m/s, so the impulse applied to this object during these 5 seconds was 8/5 kg m/s."

Student #4: "The impulse is the force F times the time t, and since we don't know the force, we can't find the impulse for this situation."

With which, if any, of these students do you agree? Explain your choice and your reasoning.

Respuesta :

Explanation:

It is given that,

Mass of object, m = 2 kg

Initial velocity, u = 3 m/s (east)

Final velocity, v = - 7 m/s (west)

The Impulse can be calculated using the change in momentum of an object i.e.

J = m(v-u)

[tex]J=2\ kg(-7\ m/s-3\ m/s)[/tex]

J = -20 kg-m/s

So, the Impulse of this object is 20 kg-m/s but the direction is opposite. Hence, statement (1) is correct i.e. Student #1: "The impulse is equal to the change in momentum, which is (2 kg)(3 m/s + 7 m/s) = 20 kg m/s."

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