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The kinetic energy of a particle continuously increases with time (A) the resultant force on the particle must be parallel to the velocity at all instants (B) the resultant force on the particle must be at an angle less than 90° all the time (C) its height above the ground level must continuously decrease (D) the magnitude of its linear momentum is increasing continuously

The kinetic energy of a particle continuously increases with time
(A) the resultant force on the particle must be parallel to the velocity at all instants
(B) the resultant force on the particle must be at an angle less than 90° all the time
(C) its height above the ground level must continuously decrease
(D) the magnitude of its linear momentum is increasing continuously

Grade:12

2 Answers

Arun
25750 Points
4 years ago
Justification for "The resultant force on the particle must be parallel to the velocity at all instants"
If resultant force is parallel to the velocity then ∣ 
V
 ∣ will increase.
∴K.E= 
2
1
​ 
 m∣ 
V
 ∣ 
2
  will increase with time.
Justification for "Its height above the ground level must continuously decreases."
Energy Cnservation:
PE 
i
​ 
 −PE 
f
​ 
 =KE 
f
​ 
 −KE 
i
​ 
 
If height decrease PE 
i
​ 
 −PE 
f
​ 
 = Increase.
∴KE 
f
​ 
 −KE 
i
​ 
 = Increase.
Where PE 
i
​ 
 = Potential energy initially.
PE 
f
​ 
 = Potential energy finally.
KE 
i
​ 
 = Kinetic Energy Initially.
KE 
f
​ 
 = Kinetic Energy Finally.
Justification for "The magnitude of its linear momentum is incease continiously."
KE= 
2
1
​ 
 V(mV)
= 
2
1
​ 
 V∣ 
P
 ∣
∴KE increases with time
Vikas TU
14149 Points
4 years ago
Dear student 
The above explanation is not understandable 
If the kinetic energy of a particle continuously increases with time, The resultant force on the particle must be at an angle less than 90∘ all the time. Hence ,the magnitude of its linear momentum increases continuously.

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