Step-by-step explanation:
It is given that,
Initially the car is at rest and travels for t₁ seconds with a uniform acceleration a₁. The driver then applies the brakes, causing a uniform acceleration a₂, If the brakes are applied for t₂ seconds.
We need to find the speed of the car just before the beginning of the braking period.
Using the formula of acceleration. It is given by :
![a_1=(v-u)/(t_1)](https://img.qammunity.org/2020/formulas/physics/college/dram49rak0pccswm13e4yiry4whbtidcj3.png)
u = 0
![v=a_1* t_1](https://img.qammunity.org/2020/formulas/physics/college/d728umy394p32ybw5tvtuaztv1za852n1g.png)
So, just before the beginning of the braking period the speed of the car is
. Hence, this is the required solution.