If the observer on Earth measures the speed of the spacecraft
as 0.700c and its length as 78.0 meters, then engineers aboard
the spacecraft measure their vehicle as 142.4 meters long.
They're both correct. There's no such thing as the spacecraft's
"real" or "proper" length.
Answer:
The velocity relative to the surface of the ice is 6.5 m/s.
Explanation:
Given that,
Mass of girl m= 45.0 kg
Mass of plank M= 150 kg
Velocity = 1.50 m/s
We need to calculate the velocity relative to the surface of the ice
Using conservation of momentum

Here,
because plank at rest

Put the value into the formula


Hence, The velocity relative to the surface of the ice is 6.5 m/s.