Question

Animal aggression. During mating season, bull elk engage in fierce fights by running head to head. Suppose a 470 kg elk running northward at 45 km/hcrashes into a 520 kg elk charging directly toward him at the same speed. The impact lasts 0.50 s, and the animals lock horns.

Part A

Find the magnitude of the velocity of the elk just after they lock horns.

Express your answer to two significant figures and include the appropriate units.

Part B

Find the magnitude of the velocity of the elk just after they lock horns.

Find the magnitude of the velocity of the elk just after they lock horns

(a) northward

(b) southward

Part C

What average force does each elk exert on the other during this collision?

Express your answer to two significant figures and include the appropriate units.

Answer 1

momentum before impact

Pinitial = m1*v1 + m2*v2

Pinitial = (470)(45) - (520)(45) = -2250 south ward

momentum after impact

Pfinal = (m1+m2)*V

Pfinal = (470 + 520)*V

total momentum is conserved

Pinitial = Pfinal

-2250 = (470 + 520)*V

V = -2.27 km/h

part(A)

magnitude of velocity = 2.3 km/h

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part B

direction = south ward

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part(c)

1 km/h = 5/18 m/s

force eerted by520 on 470 elk average force = m1*(v-v1)/t = 470*(-2.3 - 45)*(5/18)/0.5 = 12000 N

force eerted by 470 on 520 elk average force = m2*(v-v2)/t = 520*(-2.3 + 45)*(5/18)/0.5 = 12000 N