Acceleration is defined as the change in velocity per unit time. Acceleration is measured in m/s^{2}.
=
Retardation
The negative acceleration is called retardation or deceleration. Its unit is same as acceleration.
Example:
1. Car starts from rest. After 5 seconds, its velocity becomes 10 m/s. Then find its acceleration.
Initial velocity (u) = 0
Final velocity (v) = 10 m/s
Time taken (t) = 5 s
Acceleration (a) =?
Or,
Or,
∴ a = 2m/s^{2}
2. The Car which starts from the rest has an acceleration of 0.3 m/s2. After 1 minute what will be its acceleration? What is the distance travelled by car?
Initial velocity (u) = 0
Time taken (t) = 1 min= 1 × 60 s = 60 s
Acceleration (a) = 0.3 m/s^{2}
Final velocity (v) =?
Distanced travelled (s) =?
According to formula, v= u+ at
Or, v = 0 + 0.3 × 60
V= 18 m/s
∴ s =540 m
Equation of motion of uniform acceleration
Equations involving displacement, initial velocity, final velocity, acceleration and time of the motion of a moving body are equations of motion.
Considering a body moving in a straight line with uniform acceleration is shown in the figure.
Let,
Displacement = s
Initial velocity = u
Final velocity = v
Acceleration = a
Time taken = t
Relation between u, v, a and t
Or,
Or, at = v-u
∴ v= u + at ………….. (i)
This is the first equation of motion.
Relation between u,s, v and t
Or,
Or, \(\text{Average Velocity}=\frac{\text{Total Displacement(s)}}{\text{Total Time Taken(t)}}\)
Or,
As both, equation is equal
Or,
Or, 2s = (u + v)t
∴ ……………… (ii)
This is the second equation of the motion.
Relation between s, u, a and t
We already have,
V= u + at………….. (i)
s = (u + v)t…………… (ii)
Putting value of v from equation (i) in (ii)
Or,
Or, s =
Or, s = 2u×t + at × t× ½
∴ s = ut + ½ at^{2}………………. (iii)
This is the third equation of motion.
Acceleration is defined as the change in velocity per unit time. Acceleration is measured in m/s^{2}.
Solution
Initial velocity (u) = 0
Final velocity (v) = 10 m/s
Time taken (t) = 5 s
Acceleration (a) =?
Or,
Or,
∴ a = 2m/s^{2}
Solution:
Initial velocity (u) = 0
Time taken (t) = 1 min= 1 × 60 s = 60 s
Acceleration (a) = 0.3 m/s^{2}
Final velocity (v) =?
Distanced travelled (s) =?
According to formula, v= u+ at
Or, v = 0 + 0.3 × 60
V= 18 m/s
∴ s =540 m
Solution:
Or,
Or, at = v-u
∴ v= u + at ………….. (i)
This is the first equation of motion.
Or,
Or,
Or,
As both, equation is equal
Or,
Or, 2s = (u + v)t
∴ ……………… (ii)
This is the second equation of the motion.
Solution:
V= u + at………….. (i)
s = (u + v)t…………… (ii)
Putting value of v from equation (i) in (ii)
Or,
Or, s =
Or, s = 2u×t + at × t× ½
∴ s = ut + ½ at^{2}………………. (iii)
This is the third equation of motion.
Negative accelration is called ______.
deduction
reduction
retardation
induction
Velocity of car cannot be changed by ______.
changing speed and direction
Keeping speed and direction constant
Changing the direction
changing the speed
'Each and every action has its equal and opposite reaction.' Which law of motion is it?
4th law
3rd law
2nd law
1st law
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Dinesh
A car starts with an velocity of 72 km/hr and stops after 4sec' how far does the car move?
Mar 27, 2017
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ek Rana
a vehicle was at a speed of 90 km/h. on seeing a baby 20 m ahed oon the road, the driver jammed on the breaks and it came to rest at a distance of 15 m. what is its retardation and how long does it take to come at rest?
Feb 07, 2017
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