Question

given s=980t-490t^2 the velocity at the instant t=1/2

Answer 1

s=ut+1at/2
u=980
a=-980
t=1/2
v=u+at
v=980-980/2
v= 980-490
v=490
and this is not possible

Answer 2

Answer

Velocity=ds/dt=?

S=980t-490t^2

ds/dt= d/dt(980t-490t^2)

=980-980t

ds/dt =980(1-t)

As we know instant time t=1/2sec

Put 't=1/2' in above equation

ds/dt= 980(1-1/2)

=980(1/2)

V=ds/dt=490cm/sec