Periodic Motion

Question 1

what happens to the speed, velocity and acceleration when an object is moving in circular motion

Answer 1

speed is constant, it has a constant changing velocity as velocity has both magnitude and direction and it is changing direction, therefore the object is accelerating

Question 2

which direction does the centripetal force act

Answer 2

towards the center of the circle

Question 2

how do we know an object moving in circular motion must experience a force

Answer 2

from newtons firsts law - that to accelerate, an object must experience a resultant force, therefore an object moving in a circle must experience a force

Question 3

what is the force that acts on objects in circular motion

Answer 3

centripetal force

Question 4

what is the angular speed

Answer 4

the angle an object moves through per unit time

Question 4

what is a radian defined as

Answer 4

as the angle in the sector of a circle when the arc length of that sector is equal to the radius of the circle

Question 5

when does an object undergo simple harmonic motion

Answer 5

when its acceleration is directly proportional to displacement and is in the opposite direction

Question 6

what is the amplitude equal to

Answer 6

max displacement

Question 7

if a displacement time graph is a sin graph what would be the shape of a velocity time graph

Answer 7

cos graph

Question 8

if a velocity time graph was a cos graph what would be the shape of an acceleration tike graph

Answer 8

-sin graph

Question 9

what is a simple harmonic system

Answer 9

are those which oscillate with simple harmonic motion

Question 10

what are the two examples of simple harmonic motion we need to know

Answer 10

a simple pendulum and a mass-spring system

Question 11

what does the simple pendulum involve

Answer 11

a small dense bob of mass m hangs from a string of length l, which is attached to a fixed point. when the bob is displaced by a small angle (less than 10 degrees) and let it go it will oscillate with SHM

Question 12

why does the angle need to be less then 10 degrees

Answer 12

due to the derivation of the formula as a small angle approximation is used and so for larger initial angles this approximation is no longer valid and would not be a good model

Question 13

during its oscillations how is its energy transferred

Answer 13

its gravitational potential energy is transferred to kinetic energy and then back to gravitational potential energy and so on

Question 14

what are the two types of mass spring systems and what is the difference about them

Answer 14

when the spring is either vertical or horizontal. the difference is the energy which is transferred during oscillations

Question 15

how is the energy transferred in a vertical system

Answer 15

kinetic energy is converted to both elastic and gravitational potential energy

Question 16

how is the energy transferred in a horizontal system

Answer 16

kinetic energy is transferred only to elastic potential energy

Question 17

which energy is at its max when the oscillation is at its equilibrium position

Answer 17

the kinetic energy is at its max

Question 17

what happens to the total energy of a system if there is no air resistance

Answer 17

it remains constant

Question 17

what energy will be at its max when it is at the amplitude of its oscillations

Answer 17

the max amount of potential energy

Question 18

if there is air resistance how is energy lost

Answer 18

lost as heat

Question 19

what is damping

Answer 19

is where the energy is an oscillating is lost to the environment, leading to reduced amplitude of oscillations

Question 20

what are the 3 types of damping

Answer 20

light, critical, heavy

Question 21

what is light damping

Answer 21

this is also known as under-damping and this is where the amplitude gradually decreases by a small amount each oscillation

Question 22

what is heavy damping

Answer 22

also known as over-damping and this is where the amplitude reduces slower than with critical damping, but also without any additional oscillations

Question 22

what is critical damping

Answer 22

this reduces the amplitude to zero in the shortest possible time

Question 23

when do free vibrations occur

Answer 23

when no external force is continuously acting on the system, therefore the system will oscillate at its natural frequency

Question 24

what are forced vibrations

Answer 24

are where the system experiences an external driving force which causes it to oscillate, the frequency of this driving force, known as driving frequency, is significant

Question 25

what occurs when the driving frequency is equal to the natural frequency of a system

Answer 25

resonance

Question 26

what is resonance

Answer 26

is where the amplitude of oscillations of a system drastically increase due to gaining an increased amount of energy from the driving force

Question 27

what are the 3 applications of resonance

Answer 27

instruments- an instrument such as a flute has a long tube in which air resonates, causing a stationary sound wave to be formed
radio - these are tuned so that their electric circuit resonates at the same frequency as the desired broadcast frequency
swing - if someone pushes you on a swing they are providing a driving frequency, which can cause resonance if its equal to the resonant frequency and cause you to swing higher

Question 28

what is an example of a negative consequence of resonance

Answer 28

can cause damage to structure, an example is a bridge when the people crossing it are providing a driving frequency close to the natural frequency, it will begin to oscillate violently which could be very dangerous and damage the bridge

Question 29

what can reduce the effects of resonance

Answer 29

damping