PHY 2060 Lecture 20: Gravity and Pressure

Estimate the mass of a gas cloud in which pressure balances gravity for a gas temperature of and a number density of 6.00×10-2 particle per cubic centimeter.

The four masses shown in the figure are connected by massless,rigidrods.

1) Find the coordinates of the center of gravity.

2) Find the moment of inertia about an axis that passes throughmassA and is perpendicular to the page.

3) Find the moment of inertia about a diagonal axis thatpassesthrough masses B and D.

A trunk of mass 23 kg is on the floor. The trunk has a very small initial speed. The acceleration of gravity is 9.8 m/s². What constant horizontal force pushing the trunk is required to give it a velocity of 10 m/s in 20s if the coefficient of sliding friction between the trunk and the floor is 0.63?