Question

The famous Big Ben clock tower in London has hour hand of approximate length $10$ feet. Calculate the magnitude of change in velocity of the tip of the hour hand of Big Ben in $6$ hours $(1feet=0.305m)$

• A. $0.4189m/s$
• B. $0.06912m/s$
• C. $0.341m/s$
• D. $0.887mm/s$

Answer 1

The correct option is D $0.887mm/s$


The hour hand completes one rotation in $12hr$.
Thus, $\omega =\frac{2\pi }{12\times 3600}$.

In $6$ hours, the hour hand completes half rotation i.e. $\pi rad$

Change in velocity of tip is given by
$\Delta V=V_f-(-V_i)$
$=2l\omega$
$=2\times 10\times 0.305\times \frac{2\pi }{12\times 3600}$
$=0.887mm/s$.