Answer:
Most likely, it will be harder to get strong magnets to change phase because they have more density.
Answer: Force = Mass X Acceleration
F = 5 x 2
F = 10 N
1.5 m/s is the velocity.
9.3 m is the length of aisle, over which Distance will be covered.
Time is demanded in which the child will move the cart over the aisle with 1.5 m/s.
v=S/t
and,
t=S/v
Put values,
t=9.3/1.5=6.2 s