A 0.300-kg puck, initially at rest on a horizontal, frictionless surface, is str

Question

A 0.300-kg puck, initially at rest on a horizontal, frictionless surface, is struck by a 0.200-kg puck moving initially along the x axis with a speed of 2.00 m/s. After the collision, the 0.200-kg puck has a speed of 1.00 m/s at an angle of ? = 55.0° to the positive x axis (see the figure below) Before the collision li After the collision Ulf sin ? "If cos ? 02f cos ? u2f sin ? 2f (a) Determine the velocity of the 0.300-kg puck after the collision m/s (b) Find the fraction of kinetic energy transferred away or transformed to other forms of energy in the collision

Explanation / Answer

Applyint momentum conservation for the collision,

m1 v1i + m2 v2i = m1 v1f + m2 v2f

(0.300 x 0) + (0.200 x 2 i) = (0.30)(v1f) + (0.20 x 1)(cos55i + sin55j)

0.40i = 0.30 v1f + 0.115i + 0.164j

v1f = 0.95 i - 0.546j

(A) magnitude = sqrt(0.95^2 + 0.546^2) = 1.10 m/s

phi = tan^-1(0.546/0.95) = 30 deg

(B) Ki = (0.2 x 2^2 / 2) = 0.40 J  

Kf = (0.2 x 1^2 /2) + (0.3 x 1.10^2 /2)

Kf = 0.28 J  

K_lost = Ki - Kf = 0.1185 J

fraction = K_lost / Ki = 0.30

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