In outer space a rock of mass 12 kg is acted on by a constant net force 21, −11, 44 N during a 4 s time interval. At the end of this time interval the rock has a velocity of 107, 81, 104 m/s. What was the rock's velocity at the beginning of the time interval?

(100,84.67,89.33) m/s

Explanation:

From Newton's second law,

Impulse = Final momentum- initial momentum.

I = Mf-Mi Equation 1

make Mi the subject of the equation

Mi = Mf-I Equation 2

Where I = Impulse. Mf = final momentum, Mi = initial momentum.

But

I = Ft Equation 3

Where F = Force, T = time

Given: F = (21,-11,44) N, t = 4 s.

I = 4(21,-11,44)

I = (84,-44,176) N.s

Also,

Mf = mVf Equation 4

Where m = mass, Vf = Final velocity

Given: m = 12 g, Vf = (107,81,104) m/s.

Substitute into equation 4

Mf = 12(107,81,104)

Mf = (1284,972,1248) kgm/s.

Substitute the value of I and Mf into equation 2

Mi = (1284,972,1248)-(84,-44,176)

Mi = (1200,1016,1072) kgm/s

Also,

Mi = mVi

Where Vi = Initial velocity.

make Vi The subject of the equation

Vi = Mi/m  Equation 5

Given: m = 12 kg, Mi = (1200,1016,1072) kgm/s

Substitute into equation 5

Vi = (1200,1016,1072)/12

Vi = (100,84.67,89.33) m/s

explanation: magnetic pole, region at each end of a magnet where the external magnetic field is strongest. the south-seeking pole, or any pole similar to it, is called a south magnetic pole. unlike poles of different magnets attract each other; like poles repel each other.

96.77 amp

explanation:

rl = 250/100 = 2.5 ohms.

egl = 250 + (100 × 0.1) + 2 = 262 v.

at 700 r.p.m., eg2 = 262 × 700/1000 = 183.4 v.

if ia is the new current, then eg2 - 2 - (ia × 0.1) = 2.5 ia

which means this will give ia = 96.77 amp.