Physics

EQUILIBRIUM OF BODIES IN LIQUID When a heavy object is immersed in a liquid the object appears to become lighter. Consider the experience when a bucket of water is being drawn out of a well. While still under the water the bucket appears very light and becomes very heavy as soon as it is out of water. Archimedes explains this showing that when the bucket still in water, the body is acted upon by an upward force U called upthrust. While still under water, the equilibrium of the bucket is as : T = W – U. Where T =  tension in the rope.            W = weight.             U = upthrust.      U = W – T. It is also known as loss in weight. ARCHIMEDES PRINCIPLE It states that when an object is wholly or partially immersed in a fluid, it experiences a loss in weight or an upthrust which is equal to the weight of the fluid displaced by the object. FLOATING If a body is denser than the liquid, it will completely sink in it, but if the density of the body is less than that

Friction is defined as a force which acts at the surface of separation between two objects in contact and tends to oppose the motion of one over the other. It acts tangential to the surface of separation between two bodies in contact. Friction is a force of opposition. FORMS OF FRICTION (i)                  STATIC OR LIMITING FRICTION: This is the maximum force that must be overcome before a body can just start to move over another. (ii)                KINETIC OR DYNAMIC FRICTION: This is the force that must be overcome so that a body can move with uniform speed over another body. LAWS OF SOLID FRICTION (i)                  Friction opposes the relative motion between two surfaces in contact. It acts in a direction opposite to that of the motion. (ii)                The force of friction increases to the same extent as the force which tends to start the motion. (i)                   Frictional force depends on the nature of the two surfaces in contact i.e the nature of

EQUILIBRIUM OF FORCES An object is in equilibrium when it is not accelerated, that is there is no force acting on it in any direction. For a body in equilibrium, the forces acting on it are so related in magnitude and direction that no acceleration results. A body is said to be in equilibrium when the body as a whole either remains at rest or moves in a straight line with constant speed and the body is either not rotating at all or is rotating at a constant angular velocity. FORMS OF EQUILIBRIUM      (a) Static equilibrium: This is when a body is at rest or moving with constant velocity. (b) Dynamic or Kinetic equilibrium: This is when a body is moving with a constant velocity in a straight line or rotating with a constant angular velocity about a fixed axis through its centre of mass. This means that the forces that set the body in motion balance the forces that resist the motion. RESULTANT AND EQUILIBRANT FORCES A body acted upon by two or more forces is said to be in

MOTION Motion involves a change of position of a body with time. It also involves how things move and what makes them to move. There are two forms of motion: Kinematic motion which is the description of how objects move without regard to force that causing their motion and dynamic motion which deals with why objects move as they do. TYPES OF MOTION a           RANDOM MOTION: This irregular or disorder movement of object with no preferred direction. Examples are Brownian motion (irregular motion of particle of various kind suspended in water, movement of football player on the field, movement of particle suspended into the air etc. b       TRANSLATIONAL MOTION: When rigid objects move from one place to another without rotating, the motion is said to be translational. Examples are the movement of a car traveling from Sagamu to Lagos, movement from one wall of class room to another etc. c         ROTATIONAL MOTION: This is when a body in moving in circular form about i

THE CONCEPTS OF PROJECTILES Let us consider a boy who releases a piece of stone from his catapult against a bird on a tree branch, the stone will travel in parabolic path towards the bird. Likewise if we throw a tennis ball against a wall, the path of the ball towards the wall is a parabola. On hitting the wall, the ball returns to the ground also along a parabolic path. The same type of curve is seen when a ball is projected horizontally from the top of a building. The stone or ball been projected is known as PROJECTILE . EXAMPLES OF PROJECTILE MOTION (i)                  A thrown rubber ball re – bouncing from a wall. (ii)                An athlete doing the high jump. (iii)              A stone released from a catapult. (iv)              A bullet fired from a gun. MOTION OF A PROJECTILE Let us consider the simple case of a stone thrown horizontally with an initial velocity of u from the top of a high wall of height h. The stone is subject to two independent motions;