Chapter 7 gravitation View more presentations from ecphysics...
Tuesday, 20 March 2012
Sunday, 18 March 2012
Gravitation
Newton ‘s law of gravitation states that the force of attraction between particles is directly proportional to their mass and inversely proportional to the square of distance apart.
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Frictional Forces
Friction is the force opposing the motion of one body sliding or rolling over the surface of second object. Several aspects of friction are important at low velocities:
The direction of the force of friction is opposite the direction of motion.
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Equilibrium of a Rigid Body
The Moment of a Force
The moment M (turning effect) of a force about a point O is the product of the magnitude of the force (F) and the perp. distance (x)to the point of application.By convention, anti-clockwise moments are positive.
The Principle of Moments
For a rigid body acted upon by a system...
Equilibrium of Particles
Equilibrium equations for a particle: A particle is in equilibrium if the resultant of ALL forces acting on the particle is equal to zero
Equilibrium equations in component form: In a rectangular coordinate system the equilibrium equations can be represented by three scalar equations:
Triangle...
Rotational Kinetic Energy, Work and Power
Kinetic energy, work, and power are defined in rotational terms as K. E=(1/2) Iω2, W= tθ, P= tω.
Comparison of dynamics equation for linear and rotational motion. The dynamic relations are given to compare the equation for linear and rotational motion (see Table 1 ).
TABLE 1 Comparison of Dynamics Equations for Linear and Rotational Motion...
Torque and Angular Momentum
Torque
It is easier to open a door by pushing on the edge farthest from the hinges than by pushing in the middle. It is intuitive that the magnitude of the force applied and the distance from the point of application to the hinge affect the tendency of the door to rotate. This physical quantity, torque, is t = r × F sin θ, where F is the force applied, r is the distance from the point of application to the center of the rotation, and θ is...
Moment of Inertia
Substitute Newton's second law into the definition for torque with θ of 90 degrees (a right angle between F and r) and use the relationship between linear acceleration and tangential angular acceleration to obtain t = r F = rma = mr2 ( a/ r) = mr2α....
Rotational Kinematics
Rotational motion is more complicated than linear motion, and only the motion of rigid bodies will be considered here. A rigid body is an object with a mass that holds a rigid shape, such as a phonograph turntable, in contrast to the sun, which is a ball of gas. Many of the equations for the...
Centripetal Force
Centripetal force is a force that makes a body follow a curved path: it is always directed orthogonal to the velocity of the body, toward the instantaneous center of curvature of the path.
In simple terms, centripetal force is defined as a force which keeps a body moving with a uniform speed along...
Uniform Circular Motion
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