Momentum is conserved in collisions provided that A no crumpling of objects occurs B no energy is lost as heat or sound C no external forces act D no friction is involved (b) A student uses a horizontal air track to investigate collisions - Edexcel - GCSE Physics - Question 1 - 2016 - Paper 1

Since the gliders stick together after the collision, we can use conservation of momentum to find the final velocity, $v_f$:

Initial momentum = Final momentum

$m_1 v_1 + m_2 v_2 = (m_1 + m_2)v_f$

Where:

• $m_1 = 0.21 \, kg$ (mass of glider 1)
• $m_2 = 0.21 \, kg$ (mass of glider 2)
• $v_1 = 0.47 \, m/s$ (velocity of glider 1)
• $v_2 = 0 \, m/s$ (glider 2 is stationary)

Plugging in the values:
$(0.21)(0.47) + (0.21)(0) = (0.21 + 0.21)v_f$
$0.0987 = 0.42v_f$
$v_f = \frac{0.0987}{0.42} \approx 0.2357 \, m/s$