Question

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Answer 1

Given :

➳ Mass of car = 1000kg

➳ Mass of truck = 8000kg

✪ Before collision :

➳ Velocity of car = 32m/s

➳ Velocity of truck = 4m/s

✪ After collision :

➳ Velocity of car = -8m/s

(negative sign shows opposite direction.)

To Find :

➨ Velocity of truck after collision.

SoluTion :

⇒ Since, no external force acts on the whole system (car + truck), we can apply concept of momentum conservation to solve this type of questions.

⇒ Momentum is defined as the product of mass and velocity.

⇒ As per law of momentum conservation,

$\Rightarrow\tt\:Initial\:momentum=Final\:momentum\\ \\ \Rightarrow\tt\:m_1u_1+m_2u_1=m_1v_1+m_2v_2\\ \\ \Rightarrow\tt\:(1000)(32)+(8000)(4)=(1000)(-8)+(8000)v_2\\ \\ \Rightarrow\tt\:32000+32000=-8000+8000v_2\\ \\ \Rightarrow\tt\:64000+8000=8000v_2\\ \\ \Rightarrow\tt\:v_2=\dfrac{72000}{8000}\\ \\ \Rightarrow\underline{\boxed{\bf{v_2=9\:ms^{-1}}}}$

Answer 2

Correct question :

• A car of mass 1000kg travelling at 32 m/s dashes into a truck of mass 8000 kg moving in the same direction with a velocity of 4 m/s after the collision the car bounces back with velocity 8 m /s what is the Velocity of the truck after collision?

Before collision :

• mass of car(M 1) = 1000kg
• velocity of the car( V1) = 32 m/s
• mass of the truck(M 2) = 8000 kg
• velocity of the truck(V2) = 4 m /s

After collision :

• mass of car( M 1) = 1000kg
• velocity of the car (V '1)= -8 m/s
• mass of the truck(M 2) = 8000 kg
• velocity of the truck(V '2) = ??

Note :

velocity of the car is negative as it is moving in the opposite direction

Now , as no external force is acting on the system we can say that the momentum of the whole system is conserved

By applying law of conservation of momentum ,

Initial momentum = final momentum

P initial = P final

M 1( V 1 )+ M 2 (V 2 )= M 1 (V '1 )+ M 2 (V '2 )

1000 (32 ) + 8000(4) = 1000(-8)+ 8000 ( V ' 2)

32000 + 32000 = -8000+ 8000( V ' 2)

64000+ 8000 = 8000( V ' 2)

V ' 2 = 72000/8000

V ' 2 = 9

Answer :

• The velocity if the truck after collision = 9 m /s