A 2kg object accelerates as a net external force is applied to it. During the 5s

Question

A 2kg object accelerates as a net external force is applied to it. During the 5second interval that the force is applied, the object’s velocity changes from 3 m/s east to 7 m/s west.

Andre:“The impulse is equal to the change in momentum, which is (2 kg)(3 m/s + 7 m/s) = 20 kgm/s.”

Bela: “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 kgm/s.”

Carleton: “The change in momentum of this object during these 5 seconds was 8 kgm/s so the impulse applied to this object during these 5 seconds was 8/5 kgm/s.”

Dylan: “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.”

Which, if any, of these three students do you agree with?

Andre _____ Bela _____ Carleton _____ Dylan _____ None of them______

Please explain your reasoning.

Explanation / Answer

Andre:“The impulse is equal to the change in momentum, which is (2 kg)(3 m/s + 7 m/s) = 20 kg·m/s.” The impulse is the force F times the time t I=F*t I=Ma*t I=M(V-U) I= (2 kg)( 7 m/s-(-3 m/s )) = 20 kg·m/s the object’s velocity changes from 3 m/s east to 7 m/s west. MEANS NOT JUST THE MAGNITUDE OF VELOCITY IS CHANGED BUT ITS DIRECTION IS CHANGED FROM EAST TO WEST.so velocities will have opposite signs

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