Mechanics Flashcards
Define displacement.
It is distance travelled along a specific direction.
State Newton’s First Law.
A body remains in its state of rest or uniform motion in a straight line unless acted upon by a resultant force.
If F = 0, v is constant.
What is centre of gravity?
A single point where the weight of the body acts on.
When is a system in equilibrium?
Resultant force on the object is zero, and resultant torque on the system about its axis is zero.
State Archimedes’ Principle of upthrust.
When object is immersed in a fluid, it experiences an upthrust which is equal to the weight of fluid displaced by it.
Upthrust is due to pressure at the bottom of object higher than on top. Pressure difference creates upward force called upthrust.
State the principle of moments.
The sum of clockwise moments the equal to the sum of anticlockwise moments about the same axis.
What is linear momentum?
It is product of mass and velocity.
Define speed.
It is rate of change of distance.
What is impulse?
It is the product of force acting on the body and time interval during which the force is exerted.
Impulse (area under) = FΔt (graph)
What is work?
It is the product of force and the displacement in the direction of the force.
Derive potential energy changes near Earth’s surface.
W = F . S
= mg(h<sub>2</sub> - h<sub>1</sub>)
= mgh<sub>2</sub> - mgh<sub>1</sub>
= ΔGPE
What is the moment of the force?
It is the product of force and perpendicular distance between the axis of rotation and line of action of the force.
Define acceleration.
It is rate of change of velocity.
Using the definition of torque, define the torque of a couple.
Pair of forces of same magnitude but opposite in direction, producing rotation only.
Torque of couple is product of one of the forces and the perpendicular distance between their lines of action.
Recall Hooke’s Law.
Within the limit of proportionality, the extension x produced in a material is directly proportional to the load F applied.
What do you know by centripetal acceleration? How does it affect the velocity component of the object?
Resultant force acting on an object moving in circular motion directed to the centre of circular motion.
It does no work on object because it is perpendicular to velocity. It changes direction but not the magnitude of the velocity.
State Newton’s Second Law.
The rate of change of momentum of a body is proportional to the resultant force acting on it and the change takes place in the direction of the force.
F = ma
State Newton’s Third Law.
If body A exerts a force on body B, then body B exerts an equal and opposite force on body A.
FAB = - FBA
Using definition of power, derive power as product of force and velocity.
Work done per unit time.
Define velocity.
It is rate of change of displacement.
What do you know by frictional and viscous force?
They are opposing forces in opposite direction to direction of motion.
State the principle of conservation of momentum.
The total momentum of a system of objects remains constant provided no resultant external force acts on the system.
