5. Calculate the final speed of a 110-kg rugby player who is initially running at 8.00 m/s but collides head-on with a padded goal post and experiences a backward force of 1.76 x 104 N for 5.50 x 10-2 s.

0.8 m/s

Explanation:

From Newton's third law of motion,

Impulse on a body = Change in momentum of the body

Ft = m (v-u) ... Equation 1

Where F = force on the body, t = time, m = mass of the body, v = final velocity, u = initial velocity,

Note: Taking the direction of the initial velocity as negative,

Given: F = 1.76*10⁴ N, t = 5.5*10⁻² s, m = 110 kg, u = - 8.0 m/s

Substitute into equation 1

1.76*10⁴ (5.5*10⁻²) = 110[v - (-8.0) ]

968 = 110v+880

110v = 968-880

110v = 88

v = 88/110

V = 0.8 m/s

Hence the final velocity = 0.8 m/s