Posted by Vanessa on Thursday, July 10, 2008 at 1:50pm.
That formula applies only if the projectile is launched straight up. That would not be a practical way of launching an object with a catapult, unless you are doing a Monty Python movie and launching dead cows.
Unless the motion is in a straight line, as it is in this case, the rate of change of the distance away, ds/dt, is NOT the velocity.
Having said that, the rate of change of s is 30 - 9.8t m/s
Plug in t = 1 and then t=3 for the velocities they ask for.
Related Questions
Dynamics - A French artillerist, Captain A. Le Duc, developed an empirical ...
Science - Physics - When a projectile is fired horizontally, which of the ...
Physics- i need to know how to do these problems - Two projectiles are launched ...
PHYSICS - A Projectile IS FIRED FROM THE TOP OF A BUILDING WITH AN INITIAL ...
physics - a projectile is fired from the top of a building with an initial ...
Physics - Hi, i'm kinda lost with this one. a ball is thrown at 15m/s at an ...
physics - A projectile is launched at a 60 degree angle above the horizontal ...
Maths - When a ball is thrown up into the air, it makes the shape of a parabola...
math - The height of a projectile fired upward is given by the formula s = v0t &...
physics - A projectile is launched from ground level to the top of a cliff which...
For Further Reading