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Velocity of a Model Rocket

GMAT-EZCYCV

When a model rocket is launched, the propellant burns for two seconds, accelerating the rocket upward. After burnout, the rocket coasts upward for a while and then begins to fall. A small explosive charge pops out a parachute shortly after the rocket starts downward, which slows the rocket’s speed of descent. (Speed is defined as the absolute value of velocity.

This means that while velocity can be 80 feet per second for upward motion or -80 feet per second for downward motion, the speed would be 80 feet per second at both instants.) The graph below shows velocity data from the flight. Positive values of velocity indicate upward motion.

Part 1:
After how many seconds since launch did the rocket reach its highest point above the ground?


Part 2:
What is the acceleration of the rocket, in feet per square second, six seconds after launch?


Part 3:
At how many times shown is the speed of the rocket approximately 40 feet per second?