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A 50 g ball of clay traveling at speed v0 hits and sticks to a 1.0 kg brick sitting at rest on a frictionless surface.

Required:
a What is the speed of the block after the collision?
b. What percentage of the ball's initial energy is "lost"?

1 Answer

4 votes

Answer:

(a) The speed of the block after the collision is 0.0476v0.

(b) The percentage of the ball's initial energy lost, is 0 % (energy is conserved)

Step-by-step explanation:

Given;

mass of ball of clay, m₁ = 50 g = 0.05 kg

mass of brick, m₂ = 1 kg

initial velocity of the ball of clay, u₁ = v0

initial velocity of the brick, u₂ = 0

Since the clay ball sticks with the brick after collision, it is inelastic collision.

Therefore, let their final velocity = v

(a) What is the speed of the block after the collision?

Apply the principle of conservation linear momentum

m₁u₁ + m₂u₂ = v (m₁ + m₂)

0.05v₀ + 1(0) = v( 0.05 + 1)

0.05v₀ = 1.05v

v = 0.05v₀ / 1.05

v = 0.0476v₀

Thus, the speed of the block after the collision is 0.0476 of its initial velocity.

(b). What percentage of the ball's initial energy is "lost"?

Initial kinetic energy of the ball = ¹/₂mv₀²

= ¹/₂ x 0.05 x v₀²

= 0.025v₀²

Final kinetic energy of the ball, = ¹/₂(m₁ + m₂)v²

= ¹/₂ x 1.05 x 0.0476v₀²

= 0.025v₀²

Change in kinetic energy = 0.025v₀² - 0.025v₀²

= 0

percentage change in the initial kinetic energy of the ball;

= (0 / 0.025v₀²) x 100%

= 0 x 100%

= 0 %

Therefore, the percentage of the ball's initial energy lost, is 0 % (energy is conserved)

User Simon Withington
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