When someone stands against a locker and is does not moving at all, then there will be no displacement and since displacement = 0
Work done also becomes equal to zero.
Work done is usually defined as change in energy. Since the work done is zero there has been no energy used. 
 
        
             
        
        
        
Answer:
Time of flight  A is greatest
Explanation:
Let u₁ , u₂, u₃ be their initial velocity and θ₁ , θ₂ and θ₃ be their angle of projection. They all achieve a common highest height of H. 
So 
H = u₁² sin²θ₁ /2g 
H = u₂² sin²θ₂ /2g 
H = u₃² sin²θ₃ /2g
On the basis of these equation we can write
u₁ sinθ₁ =u₂ sinθ₂=u₃ sinθ₃
For maximum range we can write
D = u₁² sin2θ₁ /g 
1.5 D = u₂² sin2θ₂ / g 
2 D =u₃² sin2θ₃ / g
1.5 D / D = u₂² sin2θ₂ /u₁² sin2θ₁
1.5 = u₂ cosθ₂ /u₁ cosθ₁      ( since , u₁ sinθ₁ =u₂ sinθ₂ )
u₂ cosθ₂ >u₁ cosθ₁
u₂ sinθ₂ < u₁ sinθ₁
2u₂ sinθ₂ / g < 2u₁ sinθ₁ /g
Time of flight B < Time of flight  A
Similarly we can prove 
Time of flight C < Time of flight B
Hence Time of flight  A is greatest . 
 
        
             
        
        
        
Answer:
2653 turns
Explanation:
We are given that 
Diameter,d=2 cm
Length of magnet,l=8 cm=
1m=100 cm
Magnetic field,B=0.1 T
Current,I=2.4 A
We are given that 
Magnetic field of solenoid and magnetic are same and size of both solenoid and magnetic are also same.
Length of solenoid=
Magnetic field of solenoid

Using the formula 

Where 

 
        
             
        
        
        
Answer:

Explanation:
We first identify the elements of this simple harmonic motion:
The amplitude A is 8.8cm, because it's the maximum distance the mass can go away from the equilibrium point. In meters, it is equivalent to 0.088m.
The angular frequency ω can be calculated with the formula:

Where k is the spring constant and m is the mass of the particle.
Now, since the spring starts stretched at its maximum, the appropriate function to use is the positive cosine in the equation of simple harmonic motion:

Finally, the equation of the motion of the system is:
 
 
or 
