confirm m1 m2 m2 Two carts collide in a perfectly elastic collision. GIVEN : m:

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confirm

m1 m2 m2 Two carts collide in a perfectly elastic collision. GIVEN : m: " 8.0kg & vi, = 4,0 m/s m-4.0kg &-2.5 ms Vir 3.0 ms FIND V 6.5 m/s a. b. 1.5 m/s 4.5 m/sd. -1.5 m/s e. 3.0 m/s c. A collision is considered elastic if a. after the collision, the objects have the same shape as before the collisiorn b. the objects don't stick together. c. the objects that collide don't get warmer. d there is no lasting deformation. e all of the above A 5 kg fish swimming at a speed of 1 m/s swallows an absent-minded 1 kg fish swimming toward it at 4 m/s The speed of the larger fish after lunch is: 1 mis 4 mis a. 0.167 m/s b. 0.25 m/s c. 0.667 m/s d. 0.5 m/s e. 1.5 m/s A 1200 kg car as a speed of 20 m/s. What average force is required to stop the car in 8 s? a. 75 N b. 192 000 N 480 N 3000 N c.

Explanation / Answer

ELASTIC COLLISION

m1 = 8 kg                           m2 = 4 kg

speeds before collision

v1i = 4 m/s                       v2i = 2.5 m/s

speeds after collision

v1f = 3 m/s                        v2f = ?

initial momentum before collision

Pi = m1*v1i + m2*v2i

after collision final momentum

Pf = m1*v1f + m2*v2f

from momentum conservation

total momentum is conserved

Pf = Pi

m1*v1i + m2*v2i = m1*v1f + m2*v2f

(8*4)+(4*2.5) = (8*3) + (4*v2f)

v2f = 4.5 m/s

OPTION ( C )

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option (e)

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INELASTIC COLLISION

m1 = 5 kg                           m2 = 1 kg

speeds before collision

v1i = 1 m/s                       v2i = -4 m/s

speeds after collision

v1f = v2f = v = ?

initial momentum before collision

Pi = m1*v1i + m2*v2i

after collision final momentum

Pf = m1*v1f + m2*v2f

from momentum conservation

total momentum is conserved

Pf = Pi

m1*v1i + m2*v2i = m1*v1f + m2*v2f

(5*1) - (1*4) = (5 + 1)*v

v = 0.167 m/s

OPTION ( a )

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acceleration a ( vf - vi)/t = (0 - 20)/8 = -2.5 m/s^2

average force F = m*a = 1200*2.5 = 3000 N

OPTION ( d )

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