veer
Last Activity: 4 Years ago
The three equations of motion for an object with constant acceleration are given below.
(a) v= u+at
(b) s= ut+1/2 at2
(c) v2=u2+2as
Here u is the initial velocity, v is the final velocity, a is the acceleration , s is the displacement travelled by the body and t is the time.
Note: Take ‘+ve’ sign for a when the body accelerates and takes ‘–ve’ sign when the body decelerates.
- The displacement by the body in nth second is given by,
sn= u + a/2 (2n-1)
- Position-time (x vs t), velocity-time (v vs t) and acceleration-time (a vs t) graph for motion in one-dimension:
(i) Variation of displacement (x), velocity (v) and acceleration (a) with respect to time for different types of motion.
| Displacement(x) | Velocity(v) | Acceleration (a) |
(a) At rest | | | |
(b) Motion with constant velocity | | | |
(c) Motion with constant acceleration | | | |
(d) Motion with constant deceleration | | | |
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Scalar Quantities:- Scalar quantities are those quantities which require only magnitude for their complete specification.(e.g-mass, length, volume, density)
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Vector Quantities:- Vector quantities are those quantities which require magnitude as well as direction for their complete specification. (e.g-displacement, velocity, acceleration, force)
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Null Vector (Zero Vectors):- It is a vector having zero magnitude and an arbitrary direction.
When a null vector is added or subtracted from a given vector the resultant vector is same as the given vector.
Dot product of a null vector with any arbitrary is always zero. Cross product of a null vector with any other vector is also a null vector.
- Collinear vector:- Vectors having a common line of action are called collinear vector. There are two types.
Parallel vector (θ=0°):- Two vectors acting along same direction are called parallel vectors.
Anti parallel vector (θ=180°):-Two vectors which are directed in opposite directions are called anti-parallel vectors.
Vector addition is commutative-
Vector addition is associative-
Vector addition is distributive-
- Triangles Law of Vector addition:- If two vectors are represented by two sides of a triangle, taken in the same order, then their resultant in represented by the third side of the triangle taken in opposite order.
Magnitude of resultant vector :-
R=√(A2+B2+2ABcosθ)
Here θ is the angle between and .
If β is the angle between and ,
then,
- If three vectors acting simultaneously on a particle can be represented by the three sides of a triangle taken in the same order, then the particle will remain in equilibrium.
So,
- Parallelogram law of vector addition:-
R=√(A2+B2+2ABcosθ),
Cases 1:- When, θ=0°, then,
R= A+B (maximum), β=0°
Cases 2:- When, θ=180°, then,
R= A-B (minimum), β=0°
Cases 3:- When, θ=90°, then,
R=√(A2+B2), β = tan-1 (B/A)
- The process of subtracting one vector from another is equivalent to adding, vectorially, the negative of the vector to be subtracted.
So,
(a) Dot product or scalar product:-
,
Here A is the magnitude of , B is the magnitude of and θ is the angle between and .
(i) Perpendicular vector:-
(ii) Collinear vector:-
When, Parallel vector (θ=0°),
When, Anti parallel vector (θ=180°),
(b) Cross product or Vector product:-