P3.2.1 Centre of Mass

Question 1

Define mass.

Answer 1

Mass is the overall amount of matter an object has that is spread out throughout the object.

Question 2

What is the centre of mass?

Answer 2

A point within an object at which all the mass can be thought to be concentrated.

Question 3

How do you find the centre of mass in a symmetrical object?

Answer 3

The point where the lines of symmetry cross.

Question 4

How do you find the centre of mass in a non-symmetrical object?

Answer 4

1. Hang the object without any obstruction.
2. Hang a plumb line (string with a mass at the end) from the same point.
3. Mark the vertical line from the point to the bottom of the object, along the plumb line.
4. Repeat, hanging the object from a different point.

Centre of mass = Where the lines meet.

Question 5

What is a pendulum?

Answer 5

A mass which is suspended from a pivot that swings back and forth.

Question 6

Give 2 examples of pendulums.

Answer 6

Swings at playgrounds

Inside some clocks

Question 7

What is the time period of a pendulum?

Answer 7

The time taken for a pendulum to swing from one side to the other, and then back to its original position.

Question 8

What is the frequency of a pendulum?

Answer 8

The number of complete swings (from one side to the other and back again) made by a pendulum per second

Question 9

What is the only variable that affects the time period of a pendulum?

Answer 9

The length of the pendulum.

Question 10

How would you increase the time period of a pendulum?

Answer 10

Increase the length of the pendulum.