Physics
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Question

The roadway of a bridge over a canal is in the form of a circular arc of radius 18 m. What is the greatest speed with which a motor cycle can cross the bridge without leaving ground.

  1. square root of 98 m/s  
  2. square root of 18 cross times 9.8 end root m divided by s  
  3. 18 × 9.8 m/s  
  4. 18 / 9.8 m/s  

The correct answer is: square root of 18 cross times 9.8 end root m divided by s

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A body weight 8 g when placed in one pan and 18 g when placed on the other pan of a false balance. If the beam is horizontal when both the pans are empty. The true weight of the body is

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Let the true weight of the body be M.

As the beam is horizontal when both the pans are empty, thus net torque about the pivot is zero.
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We get  m1L1=m2L2      ....(1)
The body weighs 8g in first pan.
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Or   ML1=8L2    ....(2)        (Using (1))
The body weighs 18g in second pan.
  (18+m1)gL1=(M+m2)gL2
Or   18L1=ML2    ....(3)        (Using (1))
Dividing equation (2) and (3) we get  18M=M8
Or  M2=8×18=144
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A body weight 8 g when placed in one pan and 18 g when placed on the other pan of a false balance. If the beam is horizontal when both the pans are empty. The true weight of the body is

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Let the mass of first and second pan be m1 and m2, respectively and their respective distance from the pivot be L1 and L2.

Let the true weight of the body be M.

As the beam is horizontal when both the pans are empty, thus net torque about the pivot is zero.
  m1gL1m2gL2=0
We get  m1L1=m2L2      ....(1)
The body weighs 8g in first pan.
  (M+m1)gL1=(8+m2)gL2
Or   ML1=8L2    ....(2)        (Using (1))
The body weighs 18g in second pan.
  (18+m1)gL1=(M+m2)gL2
Or   18L1=ML2    ....(3)        (Using (1))
Dividing equation (2) and (3) we get  18M=M8
Or  M2=8×18=144
  M=12 g 
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If a body of mass m is carried by a lift moving with an upward acceleration a, then the forces acting on the body are (i) the reaction R on the floor of the lift upwards (ii) the weight m g of the body acting vertically downwards. The equation of motion will be given by


a=0 Non Inertial frame

Also, for equation of motion, we need to make it inertial.
For this, we have to acceletare in opposite direction.
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If a body of mass m is carried by a lift moving with an upward acceleration a, then the forces acting on the body are (i) the reaction R on the floor of the lift upwards (ii) the weight m g of the body acting vertically downwards. The equation of motion will be given by

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a=0 Non Inertial frame

Also, for equation of motion, we need to make it inertial.
For this, we have to acceletare in opposite direction.
 Equation of motion  is:R=mg+ma
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Assertion : First law of thermodynamics is not adequate in predicting the direction of a process
Reason : Total energy of universe is constant.

If both (A) and (R) are true but (R) is not the correct explanation of (A).

Assertion : First law of thermodynamics is not adequate in predicting the direction of a process
Reason : Total energy of universe is constant.

Chemistry-General
If both (A) and (R) are true but (R) is not the correct explanation of (A).