Forces, Moments and Hooke's Law

Forces

a push or pull acting upon an object resulting from its interaction with another object, capable of changing the object's speed, direction, or shape

Two types of forces?

contact and non-contact

Contact force

a force that acts between two objects that are physically touching each other

Non-contact force

a force that acts between two objects that are not physically touching each other

Acceleration

a change in velocity

Positive acceleration

speeding up

Negative acceleration

slowing down (deceleration)

Unit of force?

newtons (N)

Force can be measured with?

newtonmeter

Examples of contact forces?

1. friction

2. tension

3. normal contact force

Examples of non-contact forces?

1. gravitational pull

2. magnetic

3. electrostatic

Friction

is a resistance force that grips objects

Equation for speed?

s = d / t

Equation for distance?

d = s × t

Equation for time?

t = d / s

Materials that break with relatively small force can be called?

brittle

If an object is compressed or stretched too far and is unable to return to its original shape it is called?

deformed

Elastic deformation

a temporary change in a material's shape or size when subjected to force, after which it completely returns to its original dimensions once the load is removed

Hooke’s law

states that the force (F) required to extend or compress a spring by some distance (x) is directly proportional to that distance, provided the material's elastic limit is not exceeded- the formula is F = kx, where k is the spring constant (stiffness in N/m) and x is the extension/displacement.

Mechanical work

energy can be transferred from store to store by forces moving

Equation for work done?

work done W (J) = force F (N) x distance s (m)

Moments

is the turning effect of a force around a pivot

Equation for calculating moments?

moment of a force M = force F (N) × distance d (m)