Motion in a straight line practice · Mixed difficulty

The displacement of a particle is given by $y=a+b t+c t^2-d t^4$. The initial velocity and acceleration are respectively

A particle is thrown vertically up with an initial velocity $9 \mathrm{~m} / \mathrm{s}$ from the surface of Earth (take $g=10 \mathrm{~m} / \mathrm{s}^2$). The time (in seconds) taken by the particle to reach a height of $4 \mathrm{~m}$ from the surface second time (in seconds) is

A particle is constrained to move on a straight line path. It returns to the starting point after $10 \mathrm{~s}$. The total distance covered by the particle during this time is $30 \mathrm{~m}$. Which of the following statements about the motion of the particle is true?