iGCSE Physics (0625) 1.2 Motion-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
In a vacuum (no air resistance), all objects fall with the same constant acceleration $g \approx 9.8$ $m/s^{2}$, regardless of mass.
The final velocity $v$ upon hitting the ground is determined by $v = \sqrt{2gh}$, meaning higher drop heights result in higher final speeds.
Average speed for an object starting from rest is $v_{avg} = \frac{0 + v}{2}$, which is directly proportional to $\sqrt{h}$.
Since ball D is dropped from the greatest height ($4.0$ m), it will reach the highest final velocity and thus have the greatest average speed.
Mass does not affect the motion parameters in this scenario as $g$ is independent of the object’s mass.
▶️ Answer/Explanation
Detailed solution:
On a distance–time graph, the speed of an object is represented by the gradient (slope) of the line.
In Graph A, the constant gradient indicates a constant speed, while Graph B has a zero gradient, meaning the object is at rest.
In Graph C, the gradient decreases over time, which represents a decelerating object (decreasing speed).
Graph D shows a curve where the gradient becomes steeper as time progresses.
An increasing gradient directly corresponds to an increasing speed, signifying acceleration.
Therefore, Graph D is the only representation of an object moving with increasing speed.
▶️ Answer/Explanation
Detailed solution:
Acceleration is defined as the rate of change of velocity per unit time, expressed as $a = \frac{\Delta v}{\Delta t}$.
Since velocity includes both speed and direction, any change in the speed of an object results in acceleration.
Option B describes speed, not acceleration, as it refers to distance per unit time.
Option C is an incorrect physical relationship, and Option D describes weight or gravitational force ($W = mg$).
Therefore, acceleration is directly related to the changing speed (or velocity) of an object over time.
This makes statement A the only scientifically accurate description among the choices provided.