4.85 x 104.
This is the right answer.
Answer:
You would have to find the friction force of the rubber block which would be found with the equation of Normal force (mass*gravity) times cooeficient of friction which would give 8.82 N for the amount of friction and because you need more force than 8.82 N (assuming gravity is 9.8)
2a) the first sound he hears was travelling through the metal pipe (sound travels faster in solids) while the second sound he hears traveled through the air.
2b) The pipe is 330m/s * 1s = 330m.
The objects density is greater than one