Answer
(a) $0.5N/m$
(b) remains the same
(c) $0.75s$
Work Step by Step
(a) We know that
$F=Ma$
$F=\frac{Mv}{t}$
$F=\frac{M\Delta x}{t^2}$
As $F=K\Delta x$
$\implies K\Delta x=\frac{M\Delta x}{t^2}$
$\implies K=\frac{M}{t^2}$
We plug in the known values to obtain:
$K=\frac{0.28Kg}{(0.75s)^2}$
$\implies K=0.5N/m$
(b) We know that the force constant depends on the mass of the slinky and time. As the time taken by the wave to travel along the slinky doesn't depend on the stretch length, hence the time required for a way to travel along the slinky remains the same.
(c) We know that
$t=\sqrt{\frac{M\Delta x}{1.494N}}$
This simplifies to:
$t=0.75s$
