A projectile is fired straight up at a speed of 10 m/s. How long does it take to reach the top of its motion? The acceleration due to gravity is 9.8 m/s^2. Answer in units of s.

Question

A projectile is fired straight up at a speed of 10 m/s.  How long does it take to reach the top of its motion?  The acceleration due to gravity is 9.8 m/s^2.  Answer in units of s.

anonymous · Answer

have you tried what he suggested which is using the equation vfinal = vinitial + acceleration * change in time?

anonymous · Answer

then solve for t final

anonymous · Answer

isn't this time of flight as opposed to time to reach its maximum height?

anonymous · Answer

the question asks when it reaches the top of its motion, which we can say v final is zero

anonymous · Answer

got it! :)

anonymous · Answer

Why do I get -1.02 as a result?  I used 0=10+9.8t.  The time shouldn't be negative, right?

anonymous · Answer

The projectile is decelerating at a rate of 9.8 when it's thrown upward, so a=-9.8.

anonymous · Answer

and your time should now be positive