Answer:
Acoustics
Explanation: It’s the branch of physics that deals with the study of mechanical waves in gases, liquids, and solids including topics such as vibration, sound, ultrasound and infrasound.
Sector-specific technological measures – vapor recovery nozzles at gasoline pumps, cleaner-burning fuels, strong vehicle inspection programs and strict emission limits for refineries, industrial emissions and combustion sources – all can help control ozone pollution and have contributed to lower emissions over the last three decades
hope this helps
Explanation:
Given that,
Mass of the cart, 
Mass of the cart 2,
Final speed of cart 2, 
Final speed of cart 1 is 0 as it comes to rest.
Let us assume that the initial velocity of the cart 2 is 0. So using the conservation of linear momentum as :

So, the initial velocity of the 1.0-kg cart is 0.9 m/s.