Question

A car of mass 200kg travelling at 20 m/s crashes into a truck of 2000kg moving at speed 2.5m/s in the same direction of car. After the collision the car bounces back at speed of 5m/s. Find the truck's speed after the impact.

Answer 1

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Answer 2

Given:

A car of mass 200kg travelling at 20 m/s crashes into a truck of 2000kg moving at speed 2.5m/s in the same direction of car. After the collision the car bounces back at speed of 5m/s.

To find:

Truck's speed after the impact ?

Calculation:

In these type of questions , its best to apply Conservation of Momentum principle:

Let Velocity of Truck after impact be v_(t):

$\rm \therefore \: m_{c}u_{c} + m_{t}u_{t} = m_{c}v_{c} + m_{t}v_{t}$

$\rm = > \: (200)(20) + (2000)(2.5) =( 200)( - 5)+ (2000)v_{t}$

[sign of final velocity of car will be negative because the car moved in opposite direction after impact]

$\rm = > \: 4000 + 5000 = - 1000+ (2000)v_{t}$

$\rm = > \: 4000 + 5000 + 1000 = (2000)v_{t}$

$\rm = > \: 10000= (2000)v_{t}$

$\rm = > \: v_{t} = \dfrac{10000}{2000}$

$\rm = > \: v_{t} = 5 \: m {s}^{ - 1}$

So, final velocity of truck is 5 m/s in the direction of initial velocity.

Hope It Helps.