Answer:
2.5 m/s²
Step-by-step explanation:
If an object's velocity is increasing uniformly then the rate of acceleration is constant.
Constant Acceleration Equations (SUVAT)
[tex]\boxed{\begin{array}{c}\begin{aligned}v&=u+at\\\\s&=ut+\dfrac{1}{2}at^2\\\\ s&=\left(\dfrac{u+v}{2}\right)t\\\\v^2&=u^2+2as\\\\s&=vt-\dfrac{1}{2}at^2\end{aligned}\end{array}} \quad \boxed{\begin{minipage}{4.6 cm}$s$ = displacement in m\\\\$u$ = initial velocity in ms$^{-1}$\\\\$v$ = final velocity in ms$^{-1}$\\\\$a$ = acceleration in ms$^{-2}$\\\\$t$ = time in s (seconds)\end{minipage}}[/tex]
Given values:
- u = 20 m/s
- v = 30 m/s
- t = 4 s
[tex]\begin{aligned}\textsf{Using} \quad v&=u+at\\\\30&=20+4a\\30-20&=20+4a-20\\10&=4a\\4a&=10\\\dfrac{4a}{4}&=\dfrac{10}{4}\\\implies a&=2.5\; \sf m/s^2\end{aligned}[/tex]
Therefore, the magnitude of the car's average acceleration is 2.5 m/s².
