PERIODIC MOTION

Question 1

Centripetal Force Definition

Answer 1

force which acts perpendicular to the direction of the velocity, towards the centre of the circle.

Question 2

SHM

Answer 2

A type of oscillation in which the acceleration of a body is proportional to its displacement, but acts in the opposite direction

Question 3

Damping

Answer 3

decreases the amplitude of its oscillations or prevents oscillation from happening

Question 4

Resonance

Answer 4

Driving frequency = Natural frequency. Amplitude at a maximum.

Question 5

Resonance

Answer 5

Driving frequency = Natural frequency. Amplitude at a maximum.

Question 6

Sharpness of resonance

Answer 6

Increase in damping increase in sharpness of resonance

Question 7

Forced vibrations

Answer 7

Object which have their oscillation produced when a driving force is placed on it

Question 8

Free vibration system

Answer 8

objects that oscillate freely after being initially disturbed (a swing that continues moving after being used). Requires not energy transfer into or out of the mechanical system

Question 9

Closed triangle scalar drawing

Answer 9

no resultant force = equilibrium

Question 10

Parallel to slope

Answer 10

mgsin(x)

Question 11

Perpendicular to slope

Answer 11

mgcos(x)

Question 12

Discuss the motion of a ball moving in a circle at constant speed, in terms of the forces.

• Explain Newtons 3 laws
• Why is the string not horizontal

Answer 12

Ball moves in circular motion, meaning it has a constant speed (1st law), however it’s constantly changing direction. The velocity is continuously changing. Ball is accelerating.

Acceleration is in same direction as resultant force (2nd law). Force is centripetal, acts towards the centre of the circle and is equal to the tension in the string.

Ball pulls with equal and opposite force to the centripetal force, which is pulling on the ball from the centre (3rd law).

String will not be horizontal as it has a weight supported by the vertical component of the tension.

Question 13

explain why a particle is moving in a circle with uniform speed is accelerating? (2 marks)

Answer 13

Velocity of a particle is constant in magnitude but continuously changes direction, since acceleration is the rate of change of velocity the particle must therefore be accelerating.

Question 14

Tension in a string at the bottom of a circle formula

Answer 14

T = mg + mw^2r

Question 15

Phase difference between displacement with time and acceleration with time.

Answer 15

pi rad