Chapter 4 - Forces in Action Flashcards
(21 cards)
State Newton’s first law.
An object will remain in the same state of motion for as long as the forces acting on it are balanced.
State Newton’s second law.
The rate of change of momentum of an object is directly proportional to the resultant force acting on it (F=ma).
State Newton’s third law.
The force acting from body A on body B will be equal and opposite to the force acted on body A from body B.
Define 1 Newton.
The force required to accelerate a 1kg mass by 1ms^-2
What is an object’s centre of mass?
The point of an object at which we can imagine its entire mass is concentrated.
What is an object’s centre of gravity?
The point of an object at which we can imagine its entire weight is acting.
What is upthrust?
An upward buoyancy force acting on an object in a fluid.
What is normal contact force?
A force arising when one object rests against another.
What is tension?
The force within a stretched cable or rope.
What is friction?
The force that arises when two objects rub against each other.
What is drag?
A force that opposes the motion of an object in a fluid.
What factors can affect drag?
Speed, cross sectional area, and shape (maybe).
Define terminal velocity.
The constant speed that a free falling object eventually reaches when the resistance of the medium it’s falling through = its weight.
Define moment.
The turning effect of a force about some axis or point.
What is a couple?
When 2 forces are equal in size and opposite in direction, but not along the same line.
What is meant by the torque of a couple?
The turning effect created by a couple.
State the principle of moments.
For a moment in equilibrium, sum of clockwise moments = sum of anticlockwise moments.
What is density?
A measure of a substance’s mass per unit volume.
Define pressure.
Force exerted per unit area of a surface.
State Archimedes’ principle.
Upthrust = Weight of fluid displaced.
How can you calculate upthrust using pressure?
Force on the bottom of the surface - force on the top of the surface.
