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dangina [55]
3 years ago
12

A 25-kg child runs at 4.0 m/s and jumps onto a shopping cart and holds on for dear life. The cart has mass 15 kg. Assuming the c

hild rides on the cart after the collision, the speed of the child and shopping cart just after the child jumps on is:_______.
a) zero
b) 2.0 m/s
c) 3.0 m/s
d) 2.5 m/s
Physics
1 answer:
VLD [36.1K]3 years ago
5 0

Linear momentum (mass x speed) has to be conserved.

-- Momentum before the jump:

(boy's mass) x (boy's speed) = (25 kg) x (4.0 m/s) = 100 kg-m/s

(cart's mass) x (cart's speed) = (15 kg) x (zero) = zero

Total momentum before the jump:  (100 kg-m/s) + (zero) = (100 kg-m/s)

-- Momentum after the jump:

(mass of boy+cart) x (speed of boy+cart) = (40 kg) x (speed)

-- Momentum after the jump = momentum before the jump

(40 kg) x (speed) = 100 kg-m/s

Divide each side by  40 kg:

Speed = (100 kg-m/s) / (40 kg)

<em>Speed = 2.5 m/s</em>  (d)

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