Physics Notes (Forces)

Pages: 3 (665 words) Published: May 8, 2012
Physics notes

Force is an agent which produces or tends to produce motion in an object, stops or tends to stop , motion of an object

Newton's 1st law of motion:
If an object is at rest, will remain at rest until or unless an external force act on it. If an object is in motion , it continues its motion until or unless an external force act on it Newton's 1st law of motion is also called first law of inertia.

Inertia:
The tendency of an object to resist any change in its state of motion or rest is called inertia. Inertia is the measure of mass in an object.
Heavier object are difficult to bring in motion or in rest because they've greater inertia.

Newton's 2nd law of motion:
Force produces acceleration in an object in its own direction. The acceleration is directly proportional to the force and inversely proportional of the mass of the object.

Resultant force is unbalanced force.
F=ma , where F is the resultant force.

Q: the mass of a boy n his bicycle is 30kg, wants to accelerate at 1.5per sec square if the opposing force is acting on both is 40N Find the force needed for this acceleration.

Q2: a car of weight 50,000N is moving with a uniform speed of 20meters per sec The opposing force is acting on the car is 600N
Find:
a: the force applied by the engine
b: if the engine stops working, find deceleration

Q3: a car of weight 50,000N is moving on a straight road, the force applied by the engine is 2000N and the opposing forces acting on it is 800N Find acceleration

Newton's 3rd law of motion:
For every action, there is always an equal or opposite reaction " the force exerted by object A on B is always equal n opposite to the force exerted by B on A"

Friction:
When any objects slides or roles on the surface of another object which experiences a force opposite to its direction of motion. This opposing force is called Force of Friction.

Causes of friction:
If the objects are observed on the electronic microscope, the...

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