Since there are no external forces, including friction, act on the flatcar. after the sack rests on the flatcar, we would assume that momentum is conserved. This means that
total momentum of car before collision = total momentum of car after collision.
Recall,
momentum = mass x velocity
From the information given,
mass of car before collision = 2000
velocity of car before collision = 3
Thus,
total momentum of car before collision = 2000 x 3 = 6000
Also,
mass of sack = 500
mass of car and sack after collision = 500 + 2000 = 2500
velocity after collision = v
momentum after collision = 2500 x v = 2500v
Since momentum is conserved, then
6000 = 2500v
v = 6000/2500
v = 2.4
the speed of the flatcar is 2.4 m/s
Probably for kind of the same reason that speed is expressed as a
relationship between two units. You know, like miles per hour .
I guess the only reason is because no single unit has been invented
to describe density.
The rate of doing work or using energy would always be expressed
as a relationship between two units ... we would say that the rate of
work is "(so many) joules per second". But the "watt" was invented,
so we can say "(so many) watts" instead.
So I guess you're right. Density could be simpler to describe
if we only had a unit for it. Then we wouldn't have to say "(so many)
grams per cubic centimeter". We would just say "(so many) (new unit)".
Let's try it out:
"Uhhh, pardon me Professor . . . I've been working late in the lab,
and I believe I've identified a new substance, hitherto unknown to
the scientific community, and totally unexpected. In its pure form,
the substance appears to be pink, it smells like butterscotch, and
its density is approximately 27.4 Brianas. I think it's time we published
these findings ... with your name as lead investigator, of course."
I like it !
Answer:
time rising = 34 / 9.8 = 3.47 sec
total time in air = 2 * 3.47 sec = 6.94 sec
(time rising must equal time falling)
R = 17 m/s * 6.94 s = 118 m
Can also use range formula
R = v^2 sin (2 theta) / g
tan theta = 34 / 17 = 2
theta = 63.4 deg
2 theta = 126.9 deg
sin 126.9 = .8
v^2 = 17^2 + 34^2 = 1445 m^2/s^2
R = 1445 * .8 / 9.8 = 118 m agreeing with answer found above
Uhm, i'm pretty sure it's deadly.
Answer:
Mass of receiver is 92 kg
Explanation:
We have given mass of tackler 
Let the mass of receiver is 
When tackler moving alone velocity is 
m/sec
And when tackler and receiver is together velocity is 
= 2.5 m/sec
So from conservation of momentum
So mass of receiver is 92 kg
