Motion — Practice Quiz

Acceleration

Step 1: Acceleration is defined as the rate of change of velocity. Step 2: Mathematically, acceleration = (final velocity - initial velocity) / time taken. Step 3: It tells us how quickly the velocity of an object is changing. Step 4: Speed is the rate of change of distance, not velocity. Step 5: Displacement and distance are not rates of change but measurements of position or path length.

5 m/s²

Step 1: Given values - initial velocity (u) = 0 m/s (starts from rest), final velocity (v) = 20 m/s, time (t) = 4 s. Step 2: Use the formula: acceleration (a) = (v - u) / t. Step 3: Substitute values: a = (20 - 0) / 4 = 20/4. Step 4: Calculate: a = 5 m/s². Step 5: This means the car's velocity increases by 5 m/s every second.

v = u + at

Step 1: The first equation of motion relates final velocity to initial velocity, acceleration and time. Step 2: v = u + at, where v = final velocity, u = initial velocity, a = acceleration, t = time. Step 3: This equation shows that final velocity equals initial velocity plus the change in velocity (acceleration × time). Step 4: The other equations relate to displacement: s = ut + ½at² and v² = u² + 2as. Step 5: s = vt is only valid for uniform motion without acceleration.

Velocity is zero but acceleration is not zero

Step 1: At the highest point, the ball momentarily stops before falling back down, so velocity = 0. Step 2: However, gravity still acts on the ball continuously throughout its motion. Step 3: Gravitational acceleration (g ≈ 9.8 m/s²) acts downward even at the highest point. Step 4: This acceleration causes the ball to change direction and start falling back down. Step 5: If there were no acceleration at the highest point, the ball would remain there forever.