A hockey puck with mass 0.160 kg is at rest at the origin (x=0) on the horizontal, frictionless surface of the rink. At time t = 0 a player applies a force of 0.250 N to the puck, parallel to the x-axis; he continues to apply this force until t = 2.00s.

What is the position of the puck at t = 2.00s ?
In this case what is the speed of the puck?
If the same force is again applied at t = 5.00s , what is the position of the puck at t = 7.00s ?
In this case what is the speed of the puck?

a) , b) , c) , d)

Explanation:

a) Position of the puck:

The acceleration experimented by the puck is:

As the force remains constant during its time of application, accelaration is also constant. Position at given time is the following:

b) Speed of the puck:

The speed of the puck is computed as follows:

c) The absence of external force and the fact that ground is frictionless lead to the conclusion that hockey puck moves out at constant speed from 2 s. to 5 s. Then, the initial speed is:

Likewise, the initial speed is .

The new application of the same force means the return of a accelerated movement. Then:

d) The final speed of the puck is:

speed of light in vacuum is 300,000 km/s

speed of light in other mediums is given by the expression v = c/n, where c is the speed of light in vacuum and n is the refractive index of medium.

for the first medium v = 200,000 km/s

  so, refractive index of medium = 300000/200000 = 1.5

    1.5 refractive index is usually for glass. so first medium is glass.

for the second medium v = 250,00 km/s

so, refractive index of medium = 300000/250000 = 1.2

    1.2 refractive index is usually for water. so second medium is water.

for the third medium v = 0 km/s

so, refractive index of medium = 300000/0 = ∞

    ∞ refractive index is usually for opaque mediums. so third medium is opaque medium.