Question

A truck is moving with a velocity of 20m/s. The mass of truck is 100Kg.An apple of mass 0.2Kg is moving with a velocity of 5m/s. The apple falls on the trolley. What is the final velocity of apple-truck together?

Answer 1

Answer on Question #45537, Physics, Mechanics | Kinematics | Dynamics

Question:

A truck is moving with a velocity of 20m/s. The mass of truck is 100Kg. An apple of mass 0.2Kg is moving with a velocity of 5m/s. The apple falls on the trolley. What is the final velocity of apple-truck together?

Answer:

The law of conservation of momentum:

$$M v _ {t} + m v _ {a} = (M + m) u$$

where $m$ is mass of the apple, $M$ is mass of the truck, $u$ is speed of the apple and the truck together, $v_{t}$ is initial velocity of the truck, $v_{a}$ is velocity of the apple.

Therefore:

$$u = \frac {M v _ {t} + m v _ {a}}{m + M} = \frac {100 * 20 + 0.2 * 5}{100 + 0.2} = 19.97 \frac {m}{s}$$

Answer: 19.97 $\frac{m}{s}$

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