A particle moves along a straight line with equation of motion s = f(t), where s is measured in meters and t in seconds. Find the velocity and speed when t = 4.

f(t) = 50 + 40t − 4.5t^2

Question

A particle moves along a straight line with equation of motion s = f(t), where s is measured in meters and t in seconds. Find the velocity and speed when t = 4.

f(t) = 50 + 40t − 4.5t^2

ash2326 · Answer

Sorry for that guys, some troll is on rampant.

anonymous · Answer

Ok, just f(t) = 50 + 40t − 4.5t^2 the first derivate
so, f'(t)=−9t+ 40
f'(t)=−9(4)+ 40
f'(t)=−36+ 40
f'(t)= 4

If you need the aceleration is the second derivate 
f''(t)=−9

anonymous · Answer

If you're allowed to use calculus:
Velocity is the derivative of displacement:
v(t) = x'(t)
f'(t) = 40-9t
f'(4) = 40 - 9(4) = 40 - 36 = 4

and speed is just the absolute value of velocity, so also four.

anonymous · Answer

attachment

anonymous · Answer

Erick was answering the question when I started to, so I feel he deserves a medal too. so I'm gonna give you a best answer :)

anonymous · Answer

@misha511 or @Erick.04, would I be right in saying to get the derivative I have to use 
f((x+h) - f(x)) / h? I'm a little lost on setting up that derivative. 

And I wish they let you give out more than one medal :c

anonymous · Answer

Ah! Figured it out! Thanks guys