Physics, asked by aniruddhchavan523, 6 months ago

A car of mass 60 kg is moving on a road at 30 m/s. Suddenly put in neutral gear, after that its speed decreases due to air drag and other resistance forces
30
-m/s
Choose the correct statement :-
10
as V=
1 +
O
Car is uniformly accelerated in neutral gear.
Magnitude of acceleration of car is 1 m/s2 when its speed becomes 10 m/s.
0 Sum of all the resistance forces acting on car when its speed becomes 15 m/s is, 45 N.
Power needed to move the car at 10 m/s is, 100 watt.​

Answers

Answered by swatibhuktar1000
7

second is right frist is wrong

Answered by amitnrw
1

Given :  A car of mass 60kg is moving on a road at 30m/s.

Suddenly put in neutral gear, after that its speed decreases due to air drag and other resistance forces as v=30/(1+t/10)m/s.

To Find :

Choose the correct statement.

A. Car is uniformly accelerated in neutral gear.

B. Magnitude of acceleration of car is 1m/s^2 when its speed becomes 10m/s.

C. Sum of all the resistance forces acting on car when its speed becomes 15m/s is 45N.

D. Power needed to move the car at 10m/s is 100 watt

Solution :

m = 60 kg

u = 30 m/s

v=30/(1+t/10)

at t = 0 , v = 0

=> 30 = 30 / ( 1 + 0/10)  

=> 30 = 30/1

=> 30 = 30  Verified

v=30/( 1 +t/10) = 300/(10 + t)

dv/dt  =    -300/(10 + t)²

a =  -300/(10 + t)²

Acceleration is not uniform

Car is uniformly accelerated in neutral gear. INCORRECT

v=30/(1+t/10)

v = 10

=> 10  = 30/(1  + t/10)

=> 1 + t/10  = 3

=> t/10  = 2

=> t  = 20

a =  -300/(10 + t)² =  -300/( 10 + 20)²   =  -1/3 m/s²

Magnitude of acceleration of car is   -1/3 m/s² when its speed becomes 10 m/s.

Hence Magnitude of acceleration of car is 1 m/s² when its speed becomes 10 m/s  is INCORRECT

v = 15

=> => 15  = 30/(1  + t/10)

=> 1 + t/10  = 2

=> t/10  = 1

=> t  = 10

a =  -300/(10 +10)² =  -300/( 10 + 10)²   =  -3/4 m/s²

F = ma  =  60 * (-3/4)  = -45 N    ( -ve sign shows opposite force )

Sum of all the resistance forces acting on car when its speed becomes 15 m/s is,  45 N.  - CORRECT

v = 10 m/s  at  20 secs

a =  -1/3 m/s²

F = ma  = 60 (-1/3)  = -20N

Hence 20N   force v  = 10  m/s

20 * 10  = 200  W  

Power needed to move the car at 10 m/s is, 100 watt.​ is INCORRECT

Sum of all the resistance forces acting on car when its speed becomes 15 m/s is,  45 N.  - CORRECT

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