Question

A car with a mass of 1.1 x 10^3 kilograms hits a stationary truck with a mass of 2.3 x 10^3 kilograms from the rear end. The initial velocity of the car is +22.0 meters/second. After the collision the velocity of the car is -11.0 meters/second. What is the velocity of the truck after this elastic collision?

A.) +13 meters/second
B.) +20 meters/second
C.) 15.7 meters/second
D.) +7.5 meters/second
E.) +9.8 meters/second

Answer 1

If the collision is elastic then the momentum is preserved.

This implies that:

$m_aV_{oa} + m_tV_{ot} = m_aV_{fa} + m_tV_{ft}$

Where:

$m_a$ = automivil mass = $1.1 x 10 ^ 3$

$m_t$ = mass of the truck = $2.3 x 10 ^ 3$

$V_{oa}$ = initial speed of the car = +22.0 m/ s

$V_{ot}$ = initial speed of the truck = 0

$V_{fa}$ = final speed of the car = -11.0 m/ s  

$V_{ft}$ = Final speed of the truck =?

Then we clear vft

$V_{ft} = m_a\frac{(Voa-Vfa)}{m_t}$

$V_{ft} = 1.1 x 10 ^ 3 \frac{(22- (-11))}{2.3 x 10 ^ 3}$

$V_{ft} = 15.78m / s$

The answer is the sentence C...