A car of mass 2400 kg moving with a velocity of 20m/s is stopped in 10 sec on applying brakes.Calculate the retardation and the retarding force
Answers
Answer:
a = - 2 m / sec²
F = - 4800 N.
Explanation:
Given :
Mass of car = 2400 kg
Initial velocity ( u ) = 20 m / sec
When break applied final velocity become zero . v = 0
Time ( t ) = 10 sec .
From first equation :
We have :
v = u + a t
Putting values here :
0 = 20 + 10 a
10 a = - 20
a = - 2 m / sec²
Now for force we have :
F = m a
F = 2400 × - 2 N
F = - 4800 N.
Hence , we get answer.
Answers :
1.) Retardation = 2 m/s²
2.) Retarding force = 4800 N
Step by step Explanation :
Given that,
A car of mass 2400 kg moving with a velocity of 20m/s
here ,
mass of car = 2400 kg
initial velocity of the car = 20 m/s
and also given that
it is stopped in 10 sec on applying brakes.
so
final velocity of the car = 0 m/s
to find :
1.) Retardation
let the acceleration produced by brakes be a
so,
a = (v - u) /t
a = 0 - 20/10
= -2
so,
a = -2 m/s²
so,
Retardation produced by brakes = 2 m/s²
2.) Regarding force :
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1st method
Work energy theorem:
Given that,
velocity of car(v) = 20 m/s
mass(m) = 2400 kg
let the displacement of car after applying brakes be s
by the equation of motion
v² = u² + 2as
(0)² = 20² + 2(-2)s
-4s = -400
S = 400/4
S = 100 m
now,
by the work energy theorem,
Fs = ½ mv²
where
F is the retarding force
putting the values,
F(100) = ½ × 2400 × 20 × 20
F = 480000/100
F = 4800 N
so,
Retarding force = 4800 N
________________
2nd Method
Laws of motion :
Force = mass × acceleration
= 2400 × (-2)
= -4800 N
NOTE : Negation of force shows the displacement of body against the force
so
Retarding force of brakes = 4800N
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1.) Retardation = 2 m/s²
2.) Retarding force = 4800 N