Adynamite blast at a quarry launches a rock straight upward, and 2.3 s later it is rising at a rate of 13 m/s. assuming air resistance has no effect on the rock, calculate its speed (a) at launch and (b) 6.0 s after launch.

Speed at launch would be 0 m/s because it can be assumed the rock was stationery at the time of the blast, though there is no information specifying this to be true. The speed after 6 seconds would be calculated at distance over time squared. So acceleration is assumed to be 5.65m/s. After 6 seconds this would be 33.9m/s