Asst1Prob2Ver8

#$&*

course Phy 201

If the velocity of the object changes from 3 cm / sec to 11 cm / sec in 9 seconds, then at what average rate is the velocity changing?

Avg Vel = (11-3(cm/sec))/(9-0(sec)) =8/9(cm/sec^2) = .9 cm/sec^2

A ball rolling from rest down a constant incline requires 8.6 seconds to roll the 68 centimeter length of the incline.

• What is its average velocity?

Avg Vel = 68cm/8.6sec = 7.9 cm/sec

An object which accelerates uniformly from rest will attain a final velocity which is double its average velocity.

????Does this question seemed a little vague????

• What therefore is the final velocity of this ball?

The velocity will be double that of the velocity at the halfway point of its travels

'this ball' refers to the only ball mentioned up to this point, for which you calculated average velocity 7.9 cm/s.

So you can give a quantitative answer to this question.

• What average rate is the velocity of the ball therefore changing?

The velocity is doubling the average velocity.

a quantitative answer is possible here as well

An automobile accelerates uniformly down a constant incline, starting from rest. It requires 15 seconds to cover a distance of 172 meters. At what average rate is the velocity of the automobile therefore changing?

Disp=172m

Avg Vel=172m/15sec=11.5m/sec

Fin Vel= Avg Vel *2 = 23m/sec

Change in Vel = Fin Vel / Total Time

Change in Vel = (23(m/sec)/15sec) = 1.5m/sec^2

well done