Forces Flashcards
What is the unit for power in terms of SI units?
kgm^2s^-3
The principle of moments
(For a system in equilibrium) the sum of the clockwise moments (about the same point) = sum of anticlockwise moments
work done by a force
work done = force × distance moved or displacement in the direction of the force
What is a Newton?
The force when a 1 kg mass has an
acceleration of 1 ms^-2
Why can’t F=ma be applied to particles travelling at speeds close to the speed of light?
The mass of particles increases.
What is the torque of a couple?
One of the forces times the perpendicular
distance between the forces.
What is power?
The rate of work done.
State Archimedes’s principle.
The upthrust is equal to the weight of the fluid/liquid/water/air displaced.
Why will the efficiency of a mechanical device never be 100%?
This is because of thermal energy or friction.
State Newton’s 2nd law.
Resultant force is directly proportional to the rate of change of momentum.
What is drag/friction?
The force on an object which opposes the motion of the object.
What is terminal velocity?
The constant velocity of an object, achieved when the frictional forces balance the driving force.
What is weight?
The gravitational force acting on an object.
What is a couple?
A pair of equal but opposite forces with lines of action separated by a distance. Tends to produce rotation only.
What is equilibrium?
The state of an object such that the total force and total moment acting on it are zero.
What is the centre of mass/gravity?
The point where the entire weight of an object appears to act.
What is 1 Joule?
The kinetic energy a 2kg mass has when it moves with a speed of 1ms^-1.
What is the Conservation of Energy?
.
For an isolated system, the total energy is a constant value. Energy cannot be created or destroyed, only converted from one form to another.
What is 1 Watt?
The power of an engine which is converting 1J of energy in 1 second.
