Q2.A balloon rises straight up at 10 m/s. An
observer is 40 m away from the spot
where the balloon left the ground. The rate of change of the balloon’s angle of
elevation in radian per second when the balloon is 30 metres above the ground.

Q3.The position of a particle moving along a
horizontal line of any time t is
given by s (t) = 3t^{2} − 2t − 8 . The time at which the particle is at rest is

Q4.A stone is thrown up vertically. The height it
reaches at time t seconds is given by x =
80t −16t^{2} . The stone reaches the maximum height in time t seconds is given by