Question

50 points!!! Kinetics

A ball thrown vertically upward passes the same height, h, at 2s and 10s on its way up and down, respectively, Calculate h.

Answer 1

h = 98m

Step-by-step explanation:

The ball follows a projectile motion.

It it's at the same height at t = 2 and t =10,

It was at a max height at:

t = (2+10)/2

= 12/2

= 6s

Conventional: upwards positive

s = ut + ½at²

s = ut + ½(-9.8)t²

s = ut - 4.9t²

s is equal at t = 2 and t = 10

2u - 4.9(2)² = 10u - 4.9(10)²

2u - 19.6 = 10u - 490

8u = 470.4

u = 58.8

at t = 2

s = 58.8(2) - 4.9(2)²

s = 98 m

Answer 2

98 m √

Step-by-step explanation:

How about s = Vo * t + ½at² ?

s = h = Vo * 2s - 4.9m/s² * (2s)² = 2Vo - 19.6

and

h = Vo * 10s - 4.9m/s² * (10s)² = 10Vo - 490

Subtract 2nd from first:

0 = -8Vo + 470.4

Vo = 58.8 m/s

h = 58.8m/s * 2s - 4.9m/s² * (2s)² = 98 m