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April 8, 2008

Physics projectile formula

Filed under: Physics — Administrator @ 7:54 pm

A 0.11 kg ball is thrown straight up into the air with an initial velocity of 26 m/s
Find the momentum of the ball halfway to its maximum height on the way up.

V0 = 26 m/s
g=9.8 m/s^2

Max Height = V^2/2g
= 26^2 / 2*9.8
= 676 /19.6
= 34.489 meters

Halfway up is 1/2 this number or 17.2445 meters

Use the equation for height in terms of time
and solve for t

Height = Vt – 1/2 gt^2
17.2445 = 26t -1/2 (9.8)t^2
4.9t^2-26t+17.2445=0

Use the quadratic formula

( -b +- SQRT(b^2-4ac))/2a

to solve for roots

Roots are 0.777(ball on way up) and 4.52(ball on way down)

Calculate the velocity at the point when the ball is halfway to top

Use equation for velocity
V = V0 -gt
V= 26 – 9.8(0.7777)
V= 18.3854 m/s

Momentum is the product of velocity and mass

Mball x Velocity = 0.11Kg x 18.3854 m/s = 2.022 Kg *m/s

The ball will finally hit the ground 5.306 seconds after the toss
The maximum height is reached at 2.6485 seconds where the velocity is zero

Because the ball is moving fastest when first tossed, it reaches the halfway point in only 0.77 seconds but takes until 2.6 seconds to reach the maximum height.

Newtons equations of motion

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