Question

Which has more momentum, a 2000 lb car moving at 100 km/hr or a 4000 lb truck moving at 50 km/hr ?

Answer 1

The truck and car have the same momentum.

Step-by-step explanation:

`m_1` = Mass of car =
`2000\ \text{lb}=2000*0.45359237\ \text{kg}`

`v_1` = Velocity of car =
`(100)/(3.6)\ \text{m/s}`

`m_2` = Mass of truck =
`4000*0.45359237\ \text{kg}`

`v_2` = Velocity of truck =
`(50)/(3.6)\ \text{m/s}`

Momentum of car

`p_1=m_1v_1\\\Rightarrow p_1=2000*0.45359237* (100)/(3.6)\\\Rightarrow p_1=25199.58\ \text{kg m/s}`

Momentum of the truck

`p_2=m_2v_2\\\Rightarrow p_2=4000*0.45359237* (50)/(3.6)\\\Rightarrow p_2=25199.58\ \text{kg m/s}`

Both the truck and car have the same momentum of
`25199.58\ \text{kg m/s}`.