Dynamics Flashcards
Force
any action that causes a change in the physical shape or the state of motion of a body
Newtons first law of motion
body continues in its state of rest or uniform motion in a straight line, unless a resultant external force acts on it (law of inertia)
Inertia
reluctance to start moving or to change its motion once it has started
Weight
force experienced by a mass in a gravitational field
Conditions necessary for equilibrium
- resultant force on body must be 0
- resultant torque on body about any axis must be 0
Newtons third law of motion
If a body A exerts a force on body B then body B exerts an equal and opposite force on body A
Conditions to be an action reaction pair
- forces must be of the same type
- forces must act on different bodies and do not cancel each other out
just read
the forces N and W acting on the woman are equal in magnitude and opposite in direction however, they are not the same type of force and both act on the same body –> hence not an action reaction pair
Momentum
definition + formula
of a body is defined as the product of its mass, m and its velocity v
p = mv
(total momentum of the system with n bodies is p = p1 + p2 + p3 (just sum up all))
si unit: N s or kg m s-1
Newtons second law of motion
definition + formula
the rate of change of momentum of a body is proportional to the resultant force acting on it and it occurs in the direction of the force
F net = d(p)/dt = d(mv)/dt = m(dv/dt) + v(dm/dt)
when mass is constant, dm/dt is 0 and F net = m (dv/dt) = ma
Impulse
Product of a force F acting on an object ant the time for which the force acts
Principle of conservation of momentum
when bodies in a system interact, the total momentum of the system remains constant, providing no net external force acts on it
