A clock with iron pendulum keeps correct time at 15^ C . If the room temperature is 20^ C , the error in second per day will be nearly (coefficient of linear expansion of iron is =1.2 10⁻⁵ / ^ C )

Step-by-step solution

Time period of the pendulum is, T=2 l g T= 2 g l 2 l We know, l l = the change in length due to thermal expansion. T T = 1 2 l l = 1 2 Given, =1.2 10⁻⁵ / ^ C , g=9.8 ~m / s , T=86,400 ~s and T= T 2.6 sec