Definitions:
a) Uniform motion,
→ The motion of a body in which the body covers the equal distance in equal interval of time is called uniform motion.
b) Non-uniform motion.
→A motion of a body in which the body doesn't cover the equal distance in equal interval of time is called non-uniform or variable motion.
c) Displacement.
→ Displacement is the shortest distance between initial and final point travelled by a body in a particular direction.
d) Distance
→The total length covered by a body in motion is called distance.
e) Speed
→The rate of change in distance per unit time in any direction is called speed.
f) Velocity
→The rate of change in displacement per unit time in particular direction is called velocity.
Some Questions :
1). Write down the formula and S.I unit of speed.
→The formula of speed is as given below
Speed (v) = Total distance travelled/Total time taken(t)
The SI unit of speed is m/s.
2). Write down the formula and S.I unit of velocity.
→ The formula of velocity is as given below.
Velocity (v) = Displacement / time taken.
→ The SI unit of velocity is m/s.
3). Why is velocity vector quantity?
→Velocity is a vector quantity because it has both magnitude and fixed direction.
4). Why is speed a scalar quantity ?
→Speed is a scalar quantity because it has magnitude but not a fixed direction.
5). What is acceleration ? Write down its formula and SI unit.
→The rate of change in velocity per unit time is known as acceleration.
→The formula to calculate acceleration is as given below,
acceleration (a) = (V-u)/t
where,
V: final velocity
u: initial velocity
t: time taken
→The SI unit of acceleration is m/s².
6). What is retardation ? Write down the formula to calculate retardation.
→The negative value of acceleration is known as retardation.
→ The formula to calculate the retardation is as given below.
retardation (-a) = (u-v) / t
where,
V = final velocity
u=initial velocity
t=time taken.
7). Define average velocity with its formula.
→ The mean value of initial velocity and final velocity is known as average velocity.
Average velocity (V') = [Initial velocity (u) + final velocity (v)] / 2
ie. (V')= (U+v )/2
8). What do you understand by displacement-time graph ?
→The displacement time graph is a graphical representation of the relationship between the distance travelled by a body and the time taken.
9). What do you understand by velocity-time graph?
→The velocity-time graph is a graphical representation of the relationship between the velocity gained by a body and the time taken.
10). List out the different types of Newton's laws of motion.
→The different types of Newton's laws of motions are as given below:-
i) first law of motion.
ii) Second law of motion.
iii) Third law of motion.
11).Define inertia and mention its type.
→ The property of the body by the virtue of which the body is unable to change its initial state of rest or uniform motion is called inertia.
It's type are :
i) Inertia of rest
ii) Inertia of motion.
iii) Inertia of direction.
12). Define inertia of motion with 4 examples.
→If a body is in a state of motion, then it will continue to move at the same speed in the same direction unless an external force is applied to change its state. This property of a body is called inertia of motion.
Any 4 examples of inertia of motion are :
i. When a pession jumps out of a moving bus, he tends to move ahead or fall down.
ii. din athlete rury for a certain distance before taking. jump a Long
iii. The blades of the fan keep on the switch is off. moving for come time even when..
# Equations of motions.
→ There are three equations of motions. They
(1) first equation of motion.
→v=u+at
(2) Second equation of motion.
→ S= ut + 1/2 at²
(3) Third equation of motion.
→v²-u²=2as
#. Some conditions required to solve numerical problems.
→
(i) If a body starts to more from rest then its initial velocity is equal to zero (i-e. u=0m/s)
(ii) If a body comes to rest by application of external force then it's final velocity is equal to zero. (i.e. V = 0m/s)
(iii) If a body is moving with uniform velocity then the acceleration of a body is equal to zero (a= 0m/s²)
(iv) If a body is dropped down from certain height then its initial velocity is equal to zero (i.e. u=0m/s). In such conditions, a=g and s=h therefore the equations of motion would be:
* v=u+gt
* h=ut+(1/2)gt²
* v²=u²+2gh
(v) If an object is thrown vertically upwards then, its final velocity is equal to zero (i.e. v= 0m/s). In such condition a=-g and s=h so the equation of motion would be:
* v=u-gt
* h=ut-(1/2)gt²
* v²=u²-2gh