1)A closed system consists of 2 objects. Initially, object A has a momentum of 2

Question

1)A closed system consists of 2 objects. Initially, object A has a momentum of 20 kg·m/s north and object B has a momentum of 80 kg·m/s south. The two objects have a head-on collision. Afterwards, object A is observed to have a momentum of 21 kg·m/s south. After the collision, what is object B's momentum?
__ kg·m/s
And Which direction?
East
West
Up
Down
North
South
Left
Right
No direction because object B has stopped

2)A wheel is spinning at 90 rad/s. Over a period of 25 s it is spinned up to 433 rad/s.

A. Determine its angular acceleration while it was spinning up.
___rad/s2

B. Determine how many revolutions it made while spinning up.
___revolutions

Explanation / Answer

1)
20kgm/s - 80kgm/s = (momentum of B) - 21kgm/s (if north is positive)

(momentum of B) = -39kgm/s

So B is going south

2) A)angular acceleration = (angular velocity)/t

angular acceleration = (433rad/s - 90rad/s)/25s

angular acceleration = 13.72 rads/s^2

B) average angular speed = (0.5)(90rad/s + 433rad/s) = 261.5 rad/s

(261.5rads/s)(25s) = 6537.5rads

If there are 2 rads per revolution then

6537.5rads/(2rads per revolution) = 1040 revolutions

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