The horizontal distance x and the vertical height y of a projectile at a time t are given by
x=at and y=bt2+ct
where a, b and c are constants. What is the magnitude of the velocity of the projectile 1 second after it is fired?
√a2+(2b+c)2
The horizontal component of velocity is
vx=dxdt=ddt(at)=a........(1)
The vertical component of velocity is
vy=dydt=ddt(bt2+ct)=2bt+c........(2)
The value of vy at t = 1 s is (2b + c). Therefore, the magnitude of velocity at t = 1 s is
v=√(v2x+v2y)=√a2+(2b+c)2
Thus, the correct choice is (a).