Question

The bob (weight) at the end of a pendulum has a mass of 0.3 kilograms. The bob is pulled to position B and allowed to swing. It goes all the way to position C and swings back.
The potential energy of the bob at position B is >>1.47 joules. If the maximum height of the bob is 0.45 meters when it swings back, ___ joules of energy was transformed to thermal energy.
>>>>>Use g = 9.8 m/s2 and PE = m × g × h.<<<<<

It's NOT 1.323!!!

Answer 1

Answer:

0.147 J

Explanation:

The total energy that has been transformed into thermal energy is equal to the loss of gravitational potential energy between the initial situation (bob at h=0.5 m above the ground) and the final situation (bob back but at h=0.45 m above the ground).

Therefore, we have

$E_{thermal}=\Delta U=mgh_1 - mgh_2 = mg(h_1 -h_2)$

where

m = 0.3 kg is the mass of the bob

g = 9.8 m/s^2

h1 = 0.5 m is the initial height

h2 = 0.45 m is the final height

Substituting, we find the thermal energy

$E_{thermal}=(0.3 kg)(9.8 m/s^2)(0.5 m-0.45 m)=0.147 J$

Therefore, the energy transformed into thermal energy is 0.147 J.