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DIFFERENTIAL EQUATIONS - PLEASE SHOW ALL WORK AND WRITE LEGIBLY A ball with mass

ID: 1608995 • Letter: D

Question

DIFFERENTIAL EQUATIONS - PLEASE SHOW ALL WORK AND WRITE LEGIBLY

A ball with mass m kg is dropped from the roof of a building H meter high. There is a force due to air resistance with a magnitude of 0.l v^2, where the velocity v is measured in m/sec. Write down the differential equation and initial conditions that describe the motion of the ball. Write the DE in the form: dv/dt = f(t, v), and clearly identify your reference frame in terms of the direction of motion (+ vs. -). Assume the mass is 0.25 kg and the building is 30 meter high. Find the time required for the velocity of the ball to reach 4 m/sec.

Explanation / Answer

b)

as per the eauation of motion:

v = u +at

v=4 m/s

u =0

g = 9.8 m/s2

t= 0.408 seconds

a.)

the net foce acting on the ball is :

1. gravital pull = mg in favour of motion here

2. drag force = 0.1v2 in upword direction

net acceleration = (g -0.1v2/m)

dv/dt = (g -0.1v2/m)