A van traveling down a slope with a uniform acceleration of 2.15 meters/second2 attains a speed of 20.00 meters/second after 7.00 seconds. What is the initial velocity of the van?

Question

anonymous · Answer

$$v_{f}= v_{i} + a \Delta t $$

anonymous · Answer

but they don't give the final velocity

anonymous · Answer

In fact, they do! The final velocity is the 20 meters per second...

anonymous · Answer

so would it be 20 divided by acelleration plus seconds

anonymous · Answer

is the answer 4.95

johnweldon1993 · Answer

The answer is indeed 4.95m/s

anonymous · Answer

thank you.. could you help me on other questions johnweldon1993

johnweldon1993 · Answer

If I can yes, if not there are others to help :)

anonymous · Answer

ok thank you hold on

anonymous · Answer

A car with a mass of 1.1 × 103 kilograms hits a stationary truck with a mass of 2.3 × 103 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?

johnweldon1993 · Answer

So for this...It is important to see that momentum is conserved..

meaning

$$P_f = P_i$$

The momentum before is = to the momentum after
so

mass of car * Velocity of car(initially) + Mass of truck * velocity of truck(initially) = Mass of car * velocity of car(final) + Mass of truck * velocity of truck(final)

Notice you have ALL things...except for Velocity of truck (final)....so rearrange and solve for that :)

johnweldon1993 · Answer

hope that's understandable...not too used to the equation tool lol

anonymous · Answer

so it would be 22(cars mass) = -11(trucks mass)

johnweldon1993 · Answer

Not sure if you're skipping ahead but.... it would be *rearranged*

$$V_truck(final) = \frac{ M_car \times V_car(initial) + M_truck \times V_truck(initial) - M_car \times V_car(final) }{ M_truck }$$

anonymous · Answer

i don't have a calculator so this is hard

johnweldon1993 · Answer

So the velocity of the truck after the collision would be

(1.1 x 10^3kg   X   22.0m/s) + (2.3 x 10^3kg   X   0) - ( 1.1 x 10^3kg   X   -11.0m/s)
--------------------------------------------------------------------------
                                                      2.3 x 10^3

I don't have a calculator either lol so let me do this on my phone real quick...

johnweldon1993 · Answer

So what I get from doing all this out...is 15.78m/s  surprising...I thought it would be less

johnweldon1993 · Answer

Nope it's correct...just checked