Kinematics(Motion in a straight line with constant acceleration)(Problems)

1). A car travels the first half of a distance between two places at a speed of 30km/hr and second half of the distance at 50 km/hr. Find average speed of the car for the whole journey.

2). A motor car moving with a uniform speed of 20 m/s comes to a stop on the application of brakes after travelling a distance of 10 m. Find the acceleration of the car.

3). A body travels for 15 sec starting from rest with constant acceleration. If it travels distances S₁, S₂ and S₃ in the first 5 seconds, second 5 seconds and the third 5 seconds respectively, then find S₁:S₂:S₃.

4). The relation 3t=sqrt(3x) + 6 describes the displacement of a particle in one direction. Find the displacement of the particle when its velocity is zero.

5). A particle is moving eastwards with velocity of 5 m/s. In 10 sec, the velocity changes to 5 m/s northwards. Find the average acceleration.