While goofing off at the ice skating rink, a student takes off her shoes and places each of them on the ice. her friend, a hockey player, then shoots a hockey puck at each shoe. the first puck immediately comes to rest after it collides with the left shoe. the second puck rebounds after it collides with the right shoe. if each hockey puck has the same incoming speed, which shoe has greater speed after the collision?

Right shoe

Explanation:

Let the mass and velocity of incoming puck be m and v respectively.

Momentum of the colliding puck will be mv

In case of first case , the momentum of puck becomes zero so change in momentum after collision with left shoe

= mv - 0 = mv

If time duration of collision be t

rate of change of momentum

= mv / t

This is the force exerted by puck on the left shoe .

Now let us consider collision with right shoe

momentum after collision with right  shoe

- mv

change in momentum

= mv - ( - mv ) = 2mv

If time duration of collision be t

rate of change of momentum

= 2mv / t

This is the force exerted by puck on the right  shoe .

Since the force on the right shoe is more , this shoe will have greater speed

after collision.

r=rho l/a where a is the area, l is the length and rho is resistivity so the greater the area the lesser the resistance thats why the earth pin is thicker bcos current follow the shortest path, so less resistive .

b) phosphorus pentoxide