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Please help with Question(ii). I don't understand the shown step of calculating the momentum of ball B. Especially after the third line 12+Pb=15.

Please help with Question(ii). I don't understand the shown step of calculating the-example-1
User Praveen Tiwari
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1 Answer

19 votes
19 votes

Given:

m1 = mass 1 = 1kg

v1= initial velocity 1 = 12 m/s

m2= mass 2 = 3 kg

P after = momentum after collision = 15 kgm/s

(i)

Momentum of Ball A before collision

Momentum = mass x velocity

Pa = m1 v1

Replacing with the values given:

Pa = (1 kg) (12 m/s) = 12 kg m/s

(ii)

Momentum before = momentum after

Pa + Pb = P after

12 + Pb = 15

Since The ball B is travelling North, the distances travelled form a right triangle:

Apply pythagorean theorem:

c^2 = a^2 + b^2

Where c is the hypotenuse= P after = 15

a & b are the other 2 legs of the triangle = Pa and Pb

Replacing:

15^2 = 12^2 + Pb^2

Solve for Pb

15^2 - 12^2 = pb^2

√15^2 -12^2 = Pb

pb= 9 kgms^2

Please help with Question(ii). I don't understand the shown step of calculating the-example-1
User Judy T Raj
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