Question

Two blocks collide on a frictionless surface, as shown above. They have a combined mass of 10 kg and a speed of 2.5 m/s. Before the collision, one of the blocks was at rest. This block had a mass of 8 kg. What was the speed of the second block?

Answer 1

12.5 m/s

Step-by-step explanation:

Excuse my scribbles!

I had to work backwards using the inelastic collision formula for this problem.

Formula: V=(M₁V₁+M₂V₂)/(M₁+M₂)

V= Combined Speed

M₁= Block 1's Mass

V₁= Block 1's Velocity

M₂= Block 2's Mass

V₂= Block 2's Velocity

Step 1: Substitute in the values provided in the problem

• Combined mass: 10kg
• Combined speed: 2.5m/s
• Block 1's mass: 8kg
• Block 1's speed: 0

2.5=(8*0)+(?*?)/(8+?)

Step 2: Subtract block 1's mass from the combined mass to determine block 2's mass

10-8=2 Block 2's mass is 2.

2.5=(8*0)+(2*x)/(8+2)

Now simplify.

2.5=(2*x)/(8+2)

2.5=2x/10

Step 3: Multiply both sides by the reciprocal

(5)2.5=2x/10(5)

12.5=x

Answer is checked in the attached images!