Part B: Quantitative

Problems when Vf = 0

4. A 7 kg. bowling ball traveling down a test track at 8 m/s hits a pile of
dirt, and comes to a halt after 0.01 seconds.

a. Find Av and mav.

b. With what impact force did the bowling ball hit the pile of dirt?

(a)

(b)

5600 N

Explanation:

Change in velocity, is expressed as

Where v represent the velocity and subscripts f and i represent final and initial respectively. Given that the ball finally comes to rest, its final velocity is taken as 0. Substituting 0 for final velocity and the given figure of 8 m/s for initial velocity then the change in velocity is given by

To find the change in momentum, then we substitute 7 kg for m and -8 m/s for therefore

(b)

The impact force, F is equivalent to ma where m is the mass of the ball and a is the acceleration. Here, acceleration is given by dividing the change in velocity by time ie

Substituting t with 0.05 s then

Since F=ma then substituting m with 7 Kg we get that F=7*-800=-5600 N

Therefore, the impact force is equivalent to 5600 N

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.