Answer:
v1=18.46m/s
v2=29.8cm/s
Explanation:
We know that
[tex]A=10cm\\T=2s[/tex]
the equation of the motion is
[tex]x=Acos(\omega t)\\[/tex]
we can calculate w by using
[tex]\omega=\frac{2\pi}{T}=\frac{2\pi}{2}=\pi[/tex]
Hence, we have that
[tex]x=10cm*cos(\pi t)\\[/tex]
the speed will be
[tex]v=-\omega*Asin(\omega t)\\|v(0.8)|=|\pi*10cm*sin(\pi *0.8)|=18.46\frac{cm}{s}\\|v(1.4)|=|\pi*10cm*sin(\pi *1.4)|=29.8\frac{cm}{s}[/tex]
hope this helps!