# physics

posted by .

A 1-kg mass (the blue mass) is connected to a 8-kg mass (the green mass) by a massless rod 67 cm long, as shown in the figure. A hole is then drilled in the rod 40.2 cm away from the 1-kg mass, and the rod and masses are free to rotate about this pivot point, P. Calculate the period of oscillation for the masses if they are displaced slightly from the stable equilibrium position.

• physics -

The lever arm from the pivot axis to the 1 kg mass is 40.2 cm, and to the 8 kg mass is 26.8 cm. The moment of inertia about the pivot axis is
I = 1*(0.402)^2 + 8*(0.268)^2
= 0.736 kg/m^2

You will also need to know the distance L from the center of mass to the pivot axis. In this case, it is 17.23 cm = 0.1723 m. (The center of mass is 9.57 cm from the 8 kg mass).

The equation you need to use for the period can be found at
http://hyperphysics.phy-astr.gsu.edu/hbase/pendp.html

• physics -

how did you figure out distance from the center of mass?

• physics -

Require that the moment about the center of mass be zero, and solve for the location.

• physics -

if the mass is 9 kg instead of 8, would the L be 21.9

## Respond to this Question

 First Name School Subject Your Answer

## Similar Questions

1. ### physics

Two blocks, each of mass m, are attached to the ends of a massless rod which pivots as shown in Figure 8-40. Initially the rod is held in the horizontal position and then released. Calculate the magnitude and direction of the net torque …
2. ### physics

A 1-kg mass (the blue mass) is connected to a 9-kg mass (the green mass) by a massless rod 70 cm long, as shown in the figure. A hole is then drilled in the rod 40.2 cm away from the 1-kg mass, and the rod and masses are free to rotate …
3. ### physics

A 1-kg mass (the blue mass) is connected to a 9-kg mass (the green mass) by a massless rod 67 cm long, as shown in the figure. A hole is then drilled in the rod 40.2 cm away from the 1-kg mass, and the rod and masses are free to rotate …
4. ### physics

A 1-kg mass (the blue mass) is connected to a 9-kg mass (the green mass) by a massless rod 67 cm long, as shown in the figure. A hole is then drilled in the rod 40.2 cm away from the 1-kg mass, and the rod and masses are free to rotate …
5. ### physics

A 1-kg mass (the blue mass) is connected to a 9-kg mass (the green mass) by a massless rod 67 cm long, as shown in the figure. A hole is then drilled in the rod 40.2 cm away from the 1-kg mass, and the rod and masses are free to rotate …
6. ### Physics HELP!

A war-wolf, or trebuchet, is a device used during the Middle Ages to throw rocks at castles and now sometimes used to fling pumpkins and pianos. A simple trebuchet is shown in the figure. Model it as a stiff rod of negligible mass …
7. ### Physics

Two small charges with a mass of 1.0 g each are connected by 2.0-cm-long insulating rod of negligible mass. Each ball has the same magnitude of charge of 10 nC, but with opposite sign. The rod is held in a 1.0 × 104 N/C uniform electric …
8. ### Physics

A mass of 100g is attached to one end of a massless rod, 10cm in length, which is pivoted about the opposite end. The rod is held vertical, with the mass at the top, and released. The rod swings. A. What is the speed of the mass at …
9. ### physics

A war-wolf, or trebuchet, is a device used during the Middle Ages to throw rocks at castles and now sometimes used to fling pumpkins and pianos. A simple trebuchet is shown in the figure below. Model it as a stiff rod of negligible …
10. ### math

A conducting rod of mass 30 g and length 48 cm has holes drilled near each end so that it is free to slide in a vertical direction along two conducting rails as shown in the figure below. A current of 240 A is made to flow through …

More Similar Questions