Step-by-step explanation:
Using the kinematics equation,
v = u + at
where v = Final speed = 15m/s
u = Initial Speed = 30m/s
t = time taken = 10 seconds
a = acceleration.
Substitute v , u and t to find a.
[tex]15 = 30 + 10t \\ 10t = 15 - 30 \\ 10t = - 15 \\ t = - 15 \div 10 \\ = - 1.5 \frac{m}{ {s}^{2} } [/tex]