You toss your keys into the air with an initial speed of 3 m/s. How high do they go?

Question

answer the question with units i got his problem in physics and didnt know how to answer it thanks for your help

Answer 1

Apply conservation of energy.  Set the kinetic energy at the bottom equal to the potential energy at the top, and solve for the height.

 

mv²/2 = mgh ⇒

 

h = v²/(2g)

 

v = 3 m/s

g = 9.8 m/s²

 

Plug in the numbers and get h in meters.

 

You can also use the kinematic relation

 

v_f² - v² = 2ah

 

a = -g

v_f = 0

 

-v² = -2gh

 

h = v²/(2g)

 

It gives the same result.  Just plug in the numbers.