Question

a car moving at 30.0 m/s slows uniformly to a speed of 10.0 m/s in a time of 5.00 s determine the. acceleration of the car

Answer 1

Answer: $-4m/s^{2}$

Explanation:

Acceleration $a$ is defined as the variation of Velocity $\Delta V$ in time $\Delta t$ :  

$a=\frac{\Delta V}{\Delta t}$

In this case $\Delta V=10m/s - 30m/s$  and $\Delta t=5 s$.

Therefore:

$a=\frac{10m/s - 30m/s}{5 s}$

$a=\frac{-20m/s}{5 s}$

$a=-4 m/s^{2}$  Note the negative sign indicates the car is slowing