6.7. Absolute vs Relative Motion

Try these first

1. 1.

   What is the formula for absolute motion?

   Hint

   Think about how both the mass and the ground contribute to motion.

2. 2.

   Define relative motion in structural dynamics.

   Hint

   Consider what happens to a structure during earthquakes.

3. 3.

   What does absolute motion indicate?

   • Only relative displacement
   • Total displacement including ground motion
   • Only ground motion

   Hint

   Think about why both factors are essential.

4. 4.

   True or False: Engineers primarily focus on absolute motion when designing structures.

   • True
   • False

   Hint

   Focus on what is critical during seismic events.

5. 5.

   A structure experiences a ground motion of 0.5 m upward during an earthquake, and a mass within the structure moves 0.6 m upward. Calculate the absolute displacement of the mass.

   Hint

   Always remember to add the movements to find the absolute displacement.

6. 6.

   If a mass experiences a relative acceleration of 4 m/s² while the ground has an acceleration of 2 m/s², what is the absolute acceleration of the mass?

   Hint

   Combine the effects of both the mass and ground acceleration for total understanding.