A projectile launched with 200 kg*m/s of momentumand 1000J of Kenetic Eenergy whats the mass of the projectile

Question

a) 5 kg
b) 10 kg
c) 20 kg
d) 40 kg
e) 50 kg

Answer 1

Momentum 'p'=mass 'm'*velocity 'v'
p^2=m^2v^2

p^2 /2m=(1/2)mv^2 =kinetic energy K.E.

p^2 /2m =kinetic energy K.E.


mass 'm'=p^2 /2 K.E.

m=200*200 /(2*1000)=20 kg

c) is the correct answer

Answer 2

mv = 200
mv^2 = 2000
So v = mv^2 / mv = 2000 / 200 = 10 m/s
and hence m = mv / v = 200 / 10 = 20 kg.

Alternatively, you could be tricky and use m = (mv)^2 / (mv^2) = 200^2 / 2000 = 20 kg to get the mass directly without finding the velocity first, but I don't think that's as easy to follow.

Answer 3

momentum=mv=200mksunits.............(1)
Kinetic enegy=(1/2)m v^2=1000J............(2)
(2/(1) gives: (1/2)v=5or v=10m/s. put this in (1).
10m=200
so m=20kg