LO1

1. Horizontal Mass
Spring Systems
Yiwei Liu
#43934141

2. QUESTION
A wooden block and a light spring form a spring oscillator
which doing simple harmonic motion on the smooth horizontal
surface. 0 is the equilibrium position, while 1 and 2 are the
extreme left and the extreme right. A small object M which
right above the moving block will be injected into the block
and immediately left in the block to do the harmonic motion.
1 0 2
M

3. • Which statement following is correct?
• A. If M is injected into the block at position 2, the amplitude
and the period won’t change
• B. If M is injected into the block at position 1, the amplitude
won’t change, while the period will decrease
• C. If M is injected into the block at position 0, the amplitude
and the period won’t change
• D. If M is injected into the block at position 0, the amplitude
will decrease, while the period will increase

4. Answer
D

5. SOLUTION
When M is injected at 1 or 2, the maximum elastic
energy won’t change which means the vibration energy
keep the same, so the amplitude won’t change.
When M is injected at 0, there will be a loss of kinetic
energy, so the maximum kinetic energy of vibration will
be reduced which means that the vibration energy will
decrease; Therefore the amplitude will decrease.
The total mass of the oscillator will increase which
makes acceleration decrease, thus the period will
increase.