Answer:
0.15 m/s
Step-by-step explanation;
The collision is inelastic, which means only momentum is conserved.
Now, before the collision the momentum of the system is
After the collision the momentum becomes
The conservation of momentum demands that
therefore, we have
Neglecting the units for a while gives us
subtracting 0.70 from both sides gives
finally, dividing both sides by 0.19 gives and rounding the nearest hundredth gives
Hence, the velocity of the hockey puck before the collision is 0.15 m/s.