What is the following atmospheric property associated with?

weighs more

a) heated air
b) cooled air

At what time will the interfering waves have an amplitudeof zero?

Avehicle accelerates from 0 to 30 m/s in 10 seconds on a straight road

Ablock of mass m slides on a horizontal frictionless table with an initial speed v0 . it then compresses a spring of force constant k and is brought to rest. the acceleration of gravity is 9.8 m/s2 . how much is the spring compressed x from its natural length?