Question

Object starts from rest travels $20m$ in first $2$ second $A$ $160m$ in next $45s$. What will be the velocity after $7s$.

Answer 1

$s=\frac{1}{2}a{t}^2$

$20=\frac{1}{2}a{2}^2$

$a=10m/s^2$

$u=at=10\times 2=20m/s$

$s=ut+\frac{1}{2}a{t}^2$

$160=20\times 45+\frac{1}{2}a{45}^2$

$a=-0.73m/s^2$

$v=u+at=20-0.73\times 45.=-12.85m/s$

after 7 secs

$v=-12.85-(0.73\times 7)=-17.96m/s$