Question

The motion of particle is described by the equation x = a + bt², where a = 15 cm and b = 3 cm/sec². Its instant velocity at time 3 sec will be(a) 36 cm/sec(b) 9 cm/sec(c) 4.5 cm/sec(d) 18 cm/sec

Answer 1

x=a+bt^2
from derivative
dx/dt=0+2bt
dx/dt|t=3 = 2*3*3=18cm/sec