An electric clock is hanging on a wall. As you are watching the second hand rota

Question

An electric clock is hanging on a wall. As you are watching the second hand rotate, the clock's battery stops functioning, and the second hand comes to a halt over a brief period of time. Which one of the following statements correctly describes the angular velocity w and angular acceleration of the second hand as it slows down?

Can someone please explain how you got the answer as well?

A. W and a are both negative
B. W is positive and a is negative
C. W is negative and a is positive <----- That is the correct answer but WHY?
D. w and a are both positive

Explanation / Answer

The normal angular velocity of the second hand at any instant

o = - 4/60 rad /s or -60 degrees/s

The minus sign indicate that the angular velocity is in the clockwise direction

if t is the time taken for the hand to come to a stop, then using equations of motion

= o + t

= – o /t

Since the final velocity is zero

= 0-(-60)/t

=60/t degrees/s2

since t is positive acceleration is also positive

The velocity of second hand which is negative at first will increase until it reaches zero. It is evident that the velocity of the second hand is never positive

so the answer is C) W is negative and a is positive

Related Questions

Navigate

• Browse (All)
• Browse A
• Subjects

---

---

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.