Force, Mass, Momentum

Force

  • Anything that causes an object to change its velocity.

  • Only outside forces can cause velocity to change (Newton’s First Law)

SI Unit: newton (N)

  • 1 newton is force that gives 1kg an acceleration of 1ms-2.

  • Roughly equal to the weight of a 100g object.


Acceleration and Mass

  • a α Fa \alpha F

  • a α 1ma \alpha \frac{1}{m}

  • a = F(1m)a = F\left(\frac{1}{m}\right)

  • F = maF = ma


Mass

Measure of matter in an object.


Weight

Force of gravity acting on an object.


Momentum

  • mass x velocity

P=mvP = mv

SI Unit: kg m s-1


Newton’s First Law of Motion

Every body will remain in a state of rest or travelling with a constant velocity unless an unbalanced external force acts on it.


Newton’s Second Law of Motion

When an unbalanced force acts on a body the rate of change of the body’s momentum is directly proportional to the force and takes place in the direction of the force.

ΔP α F\Delta P \alpha F


Newton’s Third Law of Motion

Every action has an equal and opposite reaction


Friction

Force that opposes motion


F=mv−mut=ΔPtF=\frac{mv-mu}{t}=\frac{\Delta P}{t}


Principle of The Conservation of Momentum

m1u1+m2u2=(m1+m2)(v1+v2)=mTvTm_1u_1+m_2u_2=\left(m_1+m_2\right)\left(v_1+v_2\right)=m_{T}v_{T}