Question

A 90 kg halfback running north with a speed of 10 m/s is tackled by a 120 kg
linebacker running south at 4 m/s. The collision is perfectly inelastic. Compute
the velocity of the two players just after the tackle.​

Answer 1

Given:-

Before Collision

For halfback

• Mass of halfback ( m¹ ) = 90kg

• Initial Velocity (u¹) = 10m/s

For Linebacker

• Mass of linebacker ( m² ) = 120kg

• Initial Velocity ( u² ) = 4m/s

To Find:-

• The Velocity of two Player just after Collision.

Concept Used:-

• Conservation of Momentum.

Now,

According to Conservation of momentum.

• As the Collision is inelastic so they stucked to each other , and have Same Velocity after Collision.

→ m¹u¹ + m²u² = m¹v¹ + m²v²

→ (90) (10) + (120) (4) = (m¹ + m²)v

→ 900 + 480 = (90 + 120)v

→ 1380 = 210v

→ v = 1380/210

→ v = 6.57m/s.

Hence, The Velocity of two Players just after the Collision is 6.57m/s.

Answer 2

Answer:

2 m/s north

Explanation:

m1V1 + m2V2 = (m1 + m2)Vf

Vf = (m1V1 + m2V2)/(m1 + m2)

Vf = [(90*10) + (120*-4)]/(90 + 120)

Vf = (900 - 480)/(90 + 120)

Vf = +2 m/s (2 m/s north)