Nature and Types of Forces

Question 1

what two categories do forces fall into

Answer 1

distance and contact

Question 2

what are two examples of distance forces

Answer 2

• gravitational forces

- electrostatic forces

Question 3

what does the gravitational force between two objects depend on

Answer 3

• the mass of the objects

- and the distance between them

Question 4

what is the definition of earth’s gravitational field strength

Answer 4

the gravitational force exerted by the earth on a mass of one kilogram

Question 5

what is the equation for gravitational field strength and its value for earth

Answer 5

• g = F/m

- 9.8N/kg

Question 6

if force is equivalent to weight, what is the equation for weight

Answer 6

w = mg

Question 7

how can insulating rods be given a positive or negative charge

Answer 7

by rubbing them with woollen dusters or cotton rags

Question 8

how can the electrostatic forces produced be tested with a mini experiment

Answer 8

• suspend one rod that is charged with thread
• hold a positively and negatively charged rod on either side of the suspended rod perpendicular to it
• observe the effects

Question 9

what differentiates electrostatic forces from gravitational forces

Answer 9

• electrostatic forces can attract or repel
• resulting in pushing and pulling motions
• whereas gravitational forces usually only attract

Question 10

what other type of force acts similarly to electrostatic forces

Answer 10

• magnetic forces

- as they can also attract or repel

Question 11

what is an example of a contact force we experience all the time

Answer 11

reaction forces

Question 12

how does a reaction force actually work when you are standing on the floor

Answer 12

• when you stand on the floor your weight pushes on the floor
• the floor and your feet are in contact with each other and become slightly compressed due to it
• electrons in the atoms that make up the part of the floor youre standing on and in your feet get displaced, creating a short ranged force
• this electrostatic repulsion between your slightly positively charged feet and floor result in an upward push of the floor on you

Question 13

what happens molecularly when a rubber band is stretched

Answer 13

• the molecular separation in the band increases

- this leads to short range attractive forces between the molecules

Question 14

what state is the band in when it is stretched and why

Answer 14

• it is in a state of tension

- because the molecular forces are trying to restore the band to its original length