can anyone pls help me with any of these questions i need it asap for my finals tmrw

Answer:
Answer:2nd question answer is 2.75Explanation:
Mass of ball is missing in your 1st question.
for 2nd question,
Small cart,
m1 = 1.25kg
u1 = 2.5m/sec
v1 = -0.94m/sec ( negative sign indicate opposite motion)
Large cart,
m2 = ?
u2 = 0 m/s
v2 = 1.56 m/sec
from conservation of linear momentum,
m1*u1 + m2* u2 = m1*v1 + m2*v2
1.25*2.5 + m2*0 = 1.25*-0.94 + m2*1.56
3.125 + 0 = -1.175 + 1.56*m2
3.125 + 1.175 = 1.56*m2
4.3 = 1.56*m2
m2 = 4.3/1.56
m2 = 2.75 kg
if they stuck together instead of bounced. then,
total mass of bodies (m)= m1+m2= 4kg
final velocity of bodies (v) = ?
From , conservation of linear momentum,
m1*u1 + m2* u2 = m*v
1.25*2.5 + 2.75*0 = 4*v
3.125 = 4*v
v = 3.125/4
v = 0.78125 m/ sec.