Explanation:
Momentum before = momentum after
m₁ u₁ + m₂ u₂ = m₁ v₁ + m₂ v₂
After she jumps on the skateboard, they have the same velocity, so v₁ = v₂ = v.
m₁ u₁ + m₂ u₂ = (m₁ + m₂) v
The skateboard is originally stationary, so u₂ = 0.
m₁ u₁ = (m₁ + m₂) v
Plugging in values and solving:
(80 kg) (2 m/s) = (80 kg + 2 kg) v
v = 1.95 m/s
Round as needed.
