17 : Oscillations

Question 1

oscillating motion

Answer 1

• object starts in equilibrium position a force is applied displacing it and causes it to oscillate
• it travels towards equilibrium position at and increasing speed it slows down when it goes past equilibrium position eventually reaching max displacement (amplitude) = 0 acceleration and speed
• max acceleration at equilibrium

Question 2

displacement

Answer 2

the distance from the equilibrium position

Question 3

amplitude

Answer 3

the maximum displacement from the equilibrium position

Question 4

period

Answer 4

the time taken to complete one full oscillation

Question 5

frequency

Answer 5

the number of complete oscillations per unit time

Question 6

angular frequency

Answer 6

• ω = 2π/T
• or ω = 2πf

Question 7

simple harmonic motion

Answer 7

• oscillates either side of a midpoint
• there is always a restoring force pulling or pushing back towards. the midpoint
• size of restoring force depends on displacement and force accelerates towards the midpoint

Question 8

conditions for SMH

Answer 8

• a = ω ^2 x
• acceleration of the object is directly proportional to its displacement
• acceleration of object acts opposite direction to the displacement

Question 9

restoring force

Answer 9

• type of potential force provides restoring ( gpe for pendulums or elastic pe for spring )
• as objects moves towards the midpoint restoring force does work on object transerferring pe to ke and when moving away from midpoint ke transfers to pe
• through midpoint pe is zero and ke is max
• at max displacement ke is zero and pe is max
• sum of pe and ke = mechanical energy and stays constant

Question 10

free vibrations

Answer 10

• stretch and release mass on spring it oscillates at is natural frequency
• if no energy transfers to surroundings it will keep oscillating with the same amplitude forever

Question 11

forced vibrations

Answer 11

• forced to oscillate by a periodic external force
• the frequency of this force is called driving frequency

Question 12

resonance

Answer 12

• when driving frequency approaches natural frequency the system gains more energy from the driving force and vibrates with rapidly increasing amplitude
• driving frequency = natural frequency

Question 13

Damping

Answer 13

• any oscillating system loses energy to its surroundings
• caused usual ly by frictional forces like air resistance
• systems are deliberately damped to stop them oscillating or to minimise effect of resonance

Question 14

degree of damping

Answer 14

• damping reduces the amplitude of the oscillation over time
• critical damping reduces amplitude in the shortest possible time
• even hever daping are overdamped and take longer to return to equilibrium
• plastic deformation of ductile materials reduces the amplitude of oscillations in the same way of damping as material changes shape it absorbs energy and oscillation will become smaller

Question 15

damping affecting resonance

Answer 15

• lightly damped systems have very sharp resonance peak amplitude only increases dramatically when he driving frequency is very close to natural frequency
• heavily damped systems have a flatter response amplitude doesn’t increase much er natural frequency and aren’t as sensitive to driving frequency