2.7 Pendulums

Question 1

Name the 2 features of a simple pendulum

Answer 1

• a mass, called a bob

* a string that suspends the bob

Question 2

What happens when the Bob of a pendulum is displaced to the side and let go?

Answer 2

It oscillates back and forth, through the equilibrium position

Question 3

What is the equilibrium position of a pendulum?

Answer 3

The position of the pendulum when it stops moving

Question 4

What is the amplitude of oscillation of a pendulum?

Answer 4

The distance from the equilibrium position to the highest point on either side

Question 5

What is the time period of the oscillation of a pendulum?

Answer 5

The time taken for one complete cycle

Question 6

What is one complete cycle of an oscillation of a pendulum?

Answer 6

Time taken for the Bob to go from the highest point on one side, to the highest point on the other side and back again to the highest point on the first side

Question 7

How do we get the average for the time period of a pendulum?

Answer 7

Measure the time for 20 oscillations and divide that by 20

Question 8

What 1 thing does the time period of a pendulum depend on?

Answer 8

•the length of the pendulum

Question 9

Describe and explain the relationship between the length of the pendulum and the time period

Answer 9

As the length increases, the time period increases because it has further to travel from peak to peak

Question 10

What is the frequency of a pendulum?

Answer 10

The number of complete cycles of oscillation per second

Question 11

What happens to the frequency of a pendulum if the length of the string is increased?

Answer 11

The time period increases so the frequency decreases because it has further to travel so takes longer so less oscillations will happen in a second

Question 12

What equation relates the time period and frequency of a pendulum?

Answer 12

T=1/f

Where
T is the time period in seconds
F is the frequency in hertz

Question 13

When does the pendulums oscillation accelerate and decelerate?

Answer 13

• accelerates as it swings down as it is gaining kinetic energy as its gravitational potential energy is being transferred into kinetic energy
• decelerates as it swings up because the kinetic energy is being transferred back into gravitational potential energy and some is wasted as heat in the surroundings

Question 14

Describe and explain the effect of increasing the amplitude of a pendulum on its time period

Answer 14

Bigger amplitude will not affect the period because although the acceleration will increase as it is being let go at a bigger height, the distance it has to travel also increases so they balance out again

Question 15

Name the 2 types of energy used in pendulums

Answer 15

• gravitational potential
• kinetic
• (heat is wasted)

Question 16

In a simple pendulum where is all the mass considered to be?

Answer 16

In the Bob

Question 17

Why does a pendulum stop moving if it isn’t pushed constantly?

Answer 17

Energy is transferred due to friction at the top and air resistance

Question 18

Where is the maximum kinetic energy in a pendulum?

Answer 18

At the bottom

Question 19

Where is the maximum gp energy in a pendulum?

Answer 19

At the top of both swings

Question 20

What is the theory for a simple pendulum?

Answer 20

T=2pi (square root of L/g)

Where
T is the time period in seconds
L is the length in metres
G is gravity in newtons

Question 21

Name an example of oscillating motion

Answer 21

A pendulum moving to and fro along the same line