A 75-kilogram hockey player is skating across the ice at a speed of 6.0 meters per second. What is the magnitude of the average force required to stop the player in 0.65 second?

(1) 120 N

(2) 290 N

(3) 690 N

(4) 920 N

(3) 690 N

Explanation:

Force: This is the product of mass and acceleration of a body. The S. I unit of force is Newton (N).

The formula for force is given as,

F = ma ... Equation 1

Where F = force, m = mass, a = acceleration.

Also,

a = (v-u) / t ... Equation 2

Where v = Final velocity, u = initial velocity, t = time.

Given: u = 6.0 m/s, v = 0 m/s (bring to stop), t = 0.65 s.

Substitute into equation 2

a = (0-6) / 0.65

a = - 6/0.65

a = - 9.23 m/s²

Also given: m = 75 kg

Substitute again into equation 1

F = 75 (-9.23)

F = - 692.25 N

The negative sign tells that the force oppose the motion of the player

F ≈ 690 N

Hence the right option is (3) 690 N