15.2 Springs and SHM Flashcards Preview

A-Level Physics EDEXCEL Year 2 > 15.2 Springs and SHM > Flashcards

Flashcards in 15.2 Springs and SHM Deck (22)
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1
Q

Most springs that obey hooke’s law also obey what?

A

simple harmonic motion

2
Q

When a spring (with one fixed end and one that can be moved) is in equilibrium position what forces are acting on the movable block?

A

The reaction force and weight

3
Q

When a spring (with one fixed end and one that can be moved) is stretched what forces are acting on the movable block?

A

The reaction force,weight, force towrads equilibrium position. Although not a force the displacement is acting in the opposite direction.

4
Q

What do the 2 examples above assume?

A

The track is frictionless?

5
Q

What equation do we get when combining hooke’s law and newtons second law?

A
F=ma and F = kx 
ma = kx 
a = -k/m x  
when looking at a = -(omega)^2x 
we can see omega = square root m/k
6
Q

What equation is used to give the period of of shm of spring?

A

T = 2π(square root)m/k

7
Q

Is this equation used only for horizontally oscillating springs?

A

No, this equation can be used for vertically oscillating springs

8
Q

What does the spring need to obey to follow shm?

A

Hooke’s Law

9
Q

What is hooke’s law?

A

Extension is directly proportional to force applied.

10
Q

What needs to be met about the spring to follow this equation if it is oscillating vertically?

A

Must be light.

11
Q

What setup can we use to find the spring constant k using simple harmonic motion?

A

A workbench with a stand , which has a clamped string attached to a spring with masses. Below the spring there is a position sensor(can be replaced with a marker on ruler called the fiducial marker). Ruler is placed alongside the spring .

12
Q

How does this practical work?

A

1) Pull down the spring with the mass (this is the amplitude)
2) The masses oscillate with shm
3) The position sensor measures displacement over time
4) Create a displacement time graph and work out period (oscillations over time to get amount of oscillations per second)
5) Rearrange T = 2π(square root)m/k to get the k and substitute T and m.

13
Q

If this experiment was performed without a position sensor what would be the problem?

A

The displacement time graph wouldn’t be drawn very well

14
Q

What setup can we use to find the spring constant using hooke’s law?

A

Stand with a clamped ruler and spring with masses. Also a set square on the side

15
Q

How does this practical work?

A

1) A mass is suspended from a vertical spring
2) Use a set square to determine equilibrium position (this reduces parallax error)
3) Add mass
4) Record new h and calculate extension
5) Repeat to tabulate enough readings
6) Draw a graph of F against x, the graph should be straight line through the origin if hooke’s law is obeyed
gradient is the k (spring constant and essentially the stiffness)

16
Q

How is k changed if springs are placed next to each other and used in an experiment?

A

Multiplies k by the amount of springs placed parallel to each other

17
Q

How is k changed if springs are attatched to each other top to bottom(series)?

A

k is divided by the amount of springs

18
Q

Hence what is the equation for k in parallel and in series?

A

1/k = 1/k1 + 1/k2 in series
k = k1 + k2 in parallel
same as capacitors and opposite to resistance

19
Q

How does T change with mass?

A

Increases with mass (T^2 is proportional to m)

20
Q

How does T change with k (the spring constant )?

A

T^2 is proportional to 1/k hence decreases with k

21
Q

How does T change with amplitude?

A

It doesn’t change

22
Q

Do period and frequency depend on amplitude?

A

No, the time interval and hence frequency will not change

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