5) i dont really remember this one but i think since your uncertainty will be 0.03 so 2 significant figures is your appropriate number of sig fig
15) force X is air resistance because as the ball falls, it experiences more and more air resistance.
force Y can't be weight because W=mg and acc of free fall is constant - so there would be no variation
so it can only be resultant force and that makes sense cuz eventually it'll reach zero as constant velocity means zero acc and zero force.
18) u=30 m/s v=0 s=10
using v
2=u
2+2as we find that a deceleration of 5m/s
then if u=30m/s v=0 a=-5m/s (deceleration is negative acc)
we find that s=90m !!
20) P
o is atmospheric pressure
the child lowers it by 10% making it equal to the liquid pressure (2 enable it 2 travel up the straw)
so 0.1P
o is the liquid pressure
p is the liquid density
h is the height of the straw
and g is given as gravitational field strength
simply 0.1P
o=
pgh
so h=P
o/10
pg
22)since all spring are identical, we no 4 sure that their spring constants are all same - it's convenient if we find an expression for it so:
using F=kx
for each spring in the three spring system shown, each will experience a force of W/3
so W/3=kx
the spring constant of each spring is therefore k=W/3x
now if a force of 2W is experienced by 2 springs,
each will experience a force of only W
so for each spring W=kx' (using x' jus 2 make sure its a diff extension than before)
so x'=W/k
substitute your expression of k you end up with:
x'=3x
hope i dint confuse you
