An unwary football player collides with a padded goalpost while running at a velocity of 7.50 m/s and comes to a full stop after compressing the padding and his body 0.350 m. (a) What is his deceleration?(b) How long does the collision last?

(a) the deceleration of the player is -80.36 m/s²

(b) the time the collision last is 0.093 s

Explanation:

Given;

Initial velocity of the football player, u = 7.50 m/s

Final velocity of the football player, v = 0

distance traveled = compression of the pad, s = 0.35 m

Part (a) the deceleration of the player

v² = u² + 2as

0 = 7.5² + (2 x 0.35)a

0 = 56.25 + 0.7a

- 56.25 = 0.7a

a = -56.25 / 0.7

a = -80.36 m/s²

Part (b) the time the collision last

v = u + at

t = (v - u)/a

t = (0 - 7.5)/ -80.36

t = - 7.5 / -80.36

t = 0.093 s

the answer is the first electromagnet (a). this is because it has more coils around the ferromagnetic material. increasing the number of coils increases the surface area in which the metal interacts with the current in the coil. this enables more atoms in the metal to become aligned hence becoming more magnetized.