Question

A 500 g model train car traveling at 0.8 m/s collides with a 300 g stationary car. The cars hook up and move off down the track together. How fast are they going? ( also how do I do it )

Answer 1

Answer:

0.5 m/s

Step-by-step explanation:

A 500 g model train car traveling at 0.8 m/s collides with a 300 g stationary car.

Initial velocity of train, $v_T=0.8\ m/s$

Initial velocity of car, $v_C=0\ m/s$

Mass of train, $m_T=500\ g$

Mass of car, $m_C=300\ g$

The cars hook up and move off down the track together.

Let the final velocity of car and train, $v_T=v_C=v$

Using conservation of momentum,

Momentum before collision = Momentum after collision

$m_T\times v_T+m_C\times v_C=(m_T+m_C)\times v$

$500\times 0.8+300\times 0=(500+300)\times v$

$v=\dfrac{400}{800}$

$v=0.5\ m/s$

Hence, After collision they will going with 0.5 m/s

Answer 2

Answer:

$0.5ms^{-1}$

Step-by-step explanation:

Let v be the speed after the collision of both the cars.

Now, momentum is given by: mass × velocity, then by equating the total momentum before and after the collision of the two cars, we get

$500{\times}0.8+300{\times}0=(500+300)v$

⇒$400+0=800v$

⇒$400=800v$

⇒$v=0.5ms^{-1}$

Thus, they are moving at the velocity of $0.5ms^{-1}$