Forces: Contact And Non-Contact Forces

Question 1

Define “contact forces” and give 7 examples.

Answer 1

Contact forces: occur when 2 objects interact/are touching

E.g. Air resistance, Friction, Tension, Applied force, Spring force, Drag, Normal force

Question 2

Define “non-contact” forces and give 2 examples.

Answer 2

Non-contact forces: occurs even if objects are separated by distances
E.g. Gravity, Electrostatic force

Question 3

Define “friction”.

Answer 3

Opposes motion
The rougher the surface, the greater the force of friction
Always acts in the opposite direction to which the object is moving
No motion = no friction

Question 4

Define “applied force”

Answer 4

Applied to an object by another person/object

Question 5

Define “weight”.

Answer 5

The force that the Earth/another large planet exerts on an object
Gravity always acts “down” towards the centre of the Earth
Gravity on Earth is a constant value of 9,8 m/s or N/kg

Question 6

Define “normal force”.

Answer 6

Force that a surface exerts on an object -> object rests/moves on a surface -> surface exerts upward force
Always at right angles/90 degrees (perpendicular) to the surface

Question 7

Define “thrust”.

Answer 7

Pushes objects forward

Question 8

Define “tension”.

Answer 8

Found in cables, ropes, strings
Pulling force
Acting in opposite directions
An object is elastic when it will return to its original position and length after being exposed to tension

Question 9

Define “upthrust”.

Answer 9

Upward force that acts in water -> water resistance
Pushes object up in liquid/gas
Also called buoyancy

Question 10

Define “air resistance”.

Answer 10

Acts in the air; slows an object down
“Friction” of air
It is less if the area in contact is reduced -> streamlining