the velocity v of a projectile is a linear function of the t

the velocity v of a projectile is a linear function of the time t that it is in the air. a ball is thrown downward from the top of a building. its velocity is 42 feet per second and 74 feet per second after 2 seconds. write v as a linear fraction of t, what is the initial velocity of the projectile an what is the velocity what t=3.5 seconds?

Solution

write v as a linear fraction of t
Linear function, not fraction.
It changes 32 ft/sec in 2 seconds --> 16 ft/sec/sec
v = v0 + 16t
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The initial velocity is stated, = 42 ft/sec ??
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After 3.5 sec:
v = 42 + 16*3.5
v = 98 ft/sec