Register a domain name | Get your website designed | Get it hosted
-only @tremhost, order now

A-level: Dynamics

  • 0 Replies
  • 764 Views
*

Offline Genius

  • *
  • 20
  • +0/-0
  • I shout so that you can hear me loud and clear
    • View Profile
A-level: Dynamics
« on: December 12, 2014, 12:48:56 PM »
Newton's laws of motion: Newton's First Law
 Every body continues in a state of rest or uniform motion in a straight line unless a net (external) force acts on it.
 Newton's Second Law
 The rate of change of momentum of a body is directly proportional to the net force acting on the body, and the momentum change takes place in the direction of the net force.
 Newton's Third Law
 When object X exerts a force on object Y, object Y exerts a force of the same type that is equal in magnitude and opposite in direction on object X.
 The two forces ALWAYS act on different objects and they form an action-reaction pair.
 
 Linear momentum and its conservation: Mass: is a measure of the amount of matter in a body, & is the property of a body which resists change in motion.
Weight: is the force of gravitational attraction (exerted by the Earth) on a body.
Linear momentum: of a body is defined as the product of its mass and velocity ie p = m v
Impulse of a force (I): is defined as the product of the force and the time Δt during which it acts
ie I = F x Δt {for force which is const over the duration Δt}
For a variable force, the impulse I = Area under the F-t graph { ∫Fdt; may need to “count squares”}
 Impulse is equal in magnitude to the change in momentum of the body acted on by the force.
 Hence the change in momentum of the body is equal in mag to the area under a (net) force-time graph.
 {Incorrect to define impulse as change in momentum}
Force: is defined as the rate of change of momentum, ie F = [ m (v - u) ] / t = ma or F = v dm / dt
 The {one} Newton: is defined as the force needed to accelerate a mass of 1 kg by 1 m s-2.
Principle of Conservation of Linear Momentum: When objects of a system interact, their total momentum before and after interaction are equal if no net (external) force acts on the system.
 
  • The total momentum of an isolated system is constant
  • m1 u1 + m2 u2 = m1 v1 + m2 v2 if net F = 0 {for all collisions }
  NB: Total momentum DURING the interaction/collision is also conserved.
(Perfectly) elastic collision: Both momentum & kinetic energy of the system are conserved.
 Inelastic collision: Only momentum is conserved, total kinetic energy is not conserved.
 Perfectly inelastic collision: Only momentum is conserved, and the particles stick together after collision. (i.e. move with the same velocity.)
For all elastic collisions, u1 – u2 = v2 – v1
 ie. relative speed of approach = relative speed of separation
 or, ½ m1u12 + ½ m2u22 = ½ m1v12 + ½ m2v22
In inelastic collisions, total energy is conserved but Kinetic Energy may be converted into other forms of energy such as sound and heat energy.

 

O-level Biology: Cell Structure and Organisation

Started by Mr SmartBoard Biology

Replies: 0
Views: 1327
Last post August 26, 2014, 12:12:48 PM
by Mr Smart
O-level Chemistry: Lab Skills and Seperating Methods

Started by Mr SmartBoard Chemistry

Replies: 1
Views: 1734
Last post February 20, 2016, 06:44:36 AM
by Stayne
O-level Biology: Movement in and out of cells

Started by Mr SmartBoard Biology

Replies: 0
Views: 1216
Last post August 26, 2014, 12:18:14 PM
by Mr Smart
O-level Biology: Animal Nutrition

Started by Mr SmartBoard Biology

Replies: 0
Views: 1407
Last post September 08, 2014, 09:44:30 AM
by Mr Smart
O-level Biology: Transport in Humans

Started by Mr SmartBoard Biology

Replies: 0
Views: 1298
Last post September 08, 2014, 09:47:36 AM
by Mr Smart
O-level Biology: Plant Nutrition

Started by Mr SmartBoard Biology

Replies: 0
Views: 1319
Last post September 08, 2014, 09:49:32 AM
by Mr Smart
O-level Biology: Transport in plants

Started by Mr SmartBoard Biology

Replies: 0
Views: 1752
Last post September 08, 2014, 09:51:13 AM
by Mr Smart
O-level Biology: The Respiratory System

Started by Mr SmartBoard Biology

Replies: 1
Views: 2659
Last post December 24, 2014, 11:57:10 PM
by cialis

Shout 3.0 © 2014-2016, Shout Website by Tremmly