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

Answer:

The truck and car have the same momentum.

Explanation:

$m_1$ = Mass of car = $2000\ \text{lb}=2000\times0.45359237\ \text{kg}$

$v_1$ = Velocity of car = $\dfrac{100}{3.6}\ \text{m/s}$

$m_2$ = Mass of truck = $4000\times0.45359237\ \text{kg}$

$v_2$ = Velocity of truck = $\dfrac{50}{3.6}\ \text{m/s}$

Momentum of car

$p_1=m_1v_1\\\Rightarrow p_1=2000\times0.45359237\times \dfrac{100}{3.6}\\\Rightarrow p_1=25199.58\ \text{kg m/s}$

Momentum of the truck

$p_2=m_2v_2\\\Rightarrow p_2=4000\times0.45359237\times \dfrac{50}{3.6}\\\Rightarrow p_2=25199.58\ \text{kg m/s}$

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