first one is true, there's no net force acting on it thats greater than another or making it unbalanced, if there was the object would be in some kind of motion
All scientist use meters, that way scientist can share information across country without needing to convert the data.
3. is air resistance
4. The large rock
If you multiply m (the unit for wavelength) with 1s (the unit for frequency), you will get m/s, the unit for speed. Now multiply! 25 m/s is your final answer!
The formula for momentum is mass times velocity. Simply, we just multiply the given values:
p = mv
p = 40 kg x 4 m/s
p = 160 kg m/s
Other units for momentum is N s.
p = 160 N s
initially coin is at rest and then it drop for total time t = 1.5 s
so here the speed of the coin at which it will hit the floor is to be find

here we know that

a = 9.8 m/s^2
t = 1.5 s
now from above equation


so it will hit the floor with speed 14.7 m/s