Can anyone help me?

[SamanthaMFR]

A particle moves from point O, with displacement (in m) given by s = 4t³- 8t² (t in seconds).
Find:
a) t when It is at O again, b) The acceleration as a function of t.

I dont even know how to start this questions.

 

[Steven G]

A particle moves from point O, with displacement (in m) given by s = 4t³- 8t² (t in seconds).
Find:
a) t when It is at O again, b) The acceleration as a function of t.

I dont even know how to start this questions.

1) The S formula is the displacement formula in meters (think feet if that is more familiar for you). It tells you where you are on the number line. Part a) is just asking when it (that is s) is zero again. That leads me to believe that when t=0 (when we start) that S is also 0--hence zero again.

b) Can you think of any numerical example of acceleration??

Your car goes accelerates from 0 mph to 60 mph in 10 seconds. 'In' means divide. So in my example, 0mph to 60mph is a change in velocity and 10 seconds is the change in time. So 0 mph to 60 mph in 10 seconds is a change in velocity/change in time OR A=dV/dt.

Now can you think of an example of velocity (like speed)?

60 miles per hour is an example of velocity and is a change in distance (or displacement =S) / change in time OR V=dS/dt.

So we given the S formula. We know that V=dS/dt. We also know A= dV/dt. Put this all together to get A.

if you are having trouble understanding this then you should study algebra some more before taking on Calculus

 

[HallsofIvy]

A particle moves from point O, with displacement (in m) given by s = 4t³- 8t² (t in seconds).
Find:
a) t when It is at O again, b) The acceleration as a function of t.


I dont even know how to start this questions.

I puzzled at this. (b) is a Calculus problem: acceleration is the second derivative of displacement. But (a) just asks to solve the equation 4t³- 8t²= 0. If you have not studied Calculus you cannot hope to do (b). But if you have, it should be trivial to solve the first equation.