Mechanics Flashcards
Momentum
Is it scalar or vector?
Vector
What is impulse?
Change in momentum
What is Torque?
The total moment of a couple
What is the unit for momentum?
Kgms^-1
Define moment
The product of the force and the perpendicular distance from the point of action of the force to the axis of rotation
What happens in a partially elastic collision?
The objects move apart but have less kinetic energy than before
In projectile motion what happens in the vertical and horizontal directions?
In the horizontal there is no force on the object and therefore doesn’t accelerate.
In the vertical the object accelerates under gravity
Average velocity = ?
Displacement change/ time taken
Define displacement
The length and direction of the straight line drawn from an objects initial position
What does the gradient give you in a velocity-time graph?
The acceleration
In a velocity-time graph, what does the area under the graph give you?
The distance/displacement
What is Newton’s second law of motion?
The acceleration of a body of constant mass is related to the net external resultant force acting on the body by the equation: resultant force = m x a
Define inertia
The tendency of an object to remain in its state of rest or uniform motion in a straight line
Define centre of gravity
The single point in an object where all the weight appears to act
Define a couple
A pair of equal and opposite forces acting on a body, but not along the same line
Define acceleration
Change of velocity per unit time
What does the gradient of a the line in a distance-time graph give us?
The speed
What is Newton’s first law of motion?
A body will remain at rest or move with a constant velocity unless it is acted on by a net external resultant force
Define instantaneous velocity
The rate of change of velocity with time
What happens in a totally inelastic collision?
The objects stick together
Average acceleration equals what?
velocity change / time taken.
Define instantaneous velocity
The rate of change of displacement with time
Define distance
The length of the path moved by an object
Average speed equals what?
distance change / time taken
Define instantaneous speed
The rate of change of distance with time
What happens in an elastic collision?
No kinetic energy is lost.
Define acceleration of free fall
Acceleration of an object acted on only by the force of gravity.
What is the equation for momemtum?
m x v
What is represented by the area under a force-displacement graph?
Work done
What is the principle of conservation of momentum?
The total momentum of a system is constant provided there is no external force on the system.
Why is the time for an object to free fall independent of the object’s mass?
Force on an object = mg and acceleration = F/m = mg/m = g
Time to fall depends only on the distance and the acceleration.
