The decibel level of a jackhammer is 125 dB relative to the threshold of hearing. Determine the decibel level if three jackhammers operate side by side.

130 dB

Explanation:

The equation for decibel level is given by:

The intensity for 1 jack hammer is 3.2 W/m², therefore for 3 jack hammers, the intensity = 3 * 3.2 = 9.6 W/m²

a) 23 m/s

Explanation:

Assuming no external forces acting during the collision, total momentum must be conserved, as follows:

       

The initial momentum p₀, can be written as follows:

       

The final momentum pf, can be written as follows:

       

Since (2) and (3) are equal each other, we can solve for the only unknown that remains, v₂₀, as follows:

       

This means that the 2.0-kg object was moving at 23 m/s in a direction opposite to the 6.0-kg object, so its initial speed, before the collision, was 23.0 m/s.