MECHANICS Flashcards
If an object is less dense and has the same mass as another object what can we say about the distance travelled?
-larger volume therefore larger surface area
-therefore it will experience a greater resistive force
-do more work per unit distance/greater acceleration
-hence will travel a shorter distance.
What is an inelastic collision?
Whereby total momentum is conserved however KE is not conserved
What is an elastic collision?
Whereby total momentum and KE is conserved.
What is a person’s walking speed?
approx 1 or 2 ms^-1
What is Newton’s first law?
A body will remain stationary or move at a constant velocity unless acted upon by a resultant force.
What is Newton’s second law?
The force is directly proportional to the rate of change of momentum and acts in the same direction.
What is Newton’s third law?
Where two objects exert equal and opposite forces
What is the principle of conservation of momentum?
For a closed system the momentum remains the same before and after a collision.
What can you day about the scale diagram if it forms a closed triangle?
The object is in equilibrium.
What is a moment?
The force multiplied by the perpendicular distance from the line of action of the force to the point.
What is a couple?
A pair of coplanar forces where two forces are in equal magnitude but act in opposite directions.
What is freefall?
Where an object experiences an acceleration of ‘g’.
What is friction?
A force which opposes the motion of an object.
What happens to the air resistance as the speed of an object increases?
Air resistance increases.
What is lift?
An upwards force that acts on objects travelling in a fluid.
-acts perpendicular to the direction of fluid flow.
What is terminal speed?
Frictional forces=driving forces
-no resultant force/no acceleration therefore travelling at constant speed.
What is the relationship between initial acceleration and mass?
Initial acceleration is independent of mass.
How do you reduce friction?
Use a smoother surface or use lubricating surfaces.
When does air resistance occur?
When an object collides with air particles and transfers some of its kinetic energy to air particles as heat and sound.
How can you reduce air resistance?
-streamlining the object
-flying at a higher altitude
-reducing speed
What is the relationship between air resistance and surface area?
They are proportional.
How does a person decelerate using a parachute?
-Air resistance increases due to extra surface area
-resistive force> weight of skydiver
-sky diver decelerates (slows down)
