Physics · Motion In A Straight Line · NEET
No. Uniform velocity means velocity does not change, so acceleration is zero. Uniform acceleration means acceleration is a fixed non-zero number, so velocity keeps changing by the same amount every second. Example: free fall has uniform acceleration (g) but the velocity is never uniform - it grows by 9.8 m/s each second.
Not always. Increasing speed only tells you acceleration is present. Acceleration is uniform only if speed increases by the SAME amount each second (like 5 to 10 to 15 to 20 m/s). If speed increases by different amounts (5 to 8 to 14 to 25 m/s), the acceleration is changing, so it is non-uniform.
On a velocity-time (v-t) graph, slope = acceleration. A straight line means constant slope, so acceleration is uniform. A curved line means the slope keeps changing, so acceleration is non-uniform. So: straight v-t line = uniform, curved v-t line = non-uniform.
No. The three equations of motion (v = u + at, s = ut + (1/2)at2, v2 = u2 + 2as) are derived assuming a is constant. If acceleration changes with time, these give wrong answers. For non-uniform acceleration you must use calculus: a = dv/dt and integrate, or work from the given equation.
Free fall (ignoring air resistance) is uniform acceleration because g stays constant at about 9.8 m/s2 in value and always points downward. Even though the ball speeds up while falling and slows down while rising, the acceleration value never changes, so it is uniform.
The relation between time t and position x of a particle moving along a straight line is given by t = x^2 + x. The acceleration of the particle is:
If the velocity of a particle is v = At + Bt^2, where A and B are constants, then the distance travelled by it between 1 s and 2 s is:
Try the real previous-year questions from this chapter — each with the answer and a full solution.
Uniform acceleration means the acceleration keeps the same value and same direction all the time. The velocity increases (or decreases) by the same amount every second. Free fall under gravity is the classic example, with a = g = 9.8 m/s2.
Non-uniform acceleration means the acceleration changes with time - either its size or its direction (or both). The velocity does not change by equal steps. A car speeding up in city traffic is a real example.
The three kinematic equations - v = u + at, s = ut + (1/2)at2, and v2 = u2 + 2as - are valid ONLY for uniform (constant) acceleration. For non-uniform acceleration you must use calculus (a = dv/dt) or the area/slope of graphs.
Look at the velocity-time graph. A straight line means uniform acceleration (constant slope). A curved line means non-uniform acceleration (changing slope). On an acceleration-time graph, uniform acceleration is a horizontal line, and non-uniform is a sloping or curved line.
NEET often gives you a position or velocity written as an equation of t or x. If the acceleration turns out to depend on t or x, it is non-uniform and you must differentiate/integrate - using v = u + at there is a guaranteed wrong answer. Spotting uniform vs non-uniform tells you which method to use.
