iGCSE Physics (0625) 1.6 Momentum-Exam Style Questions- New Syllabus
▶️ Answer/Explanation
Detailed solution:
Initial momentum is $p_{i} = mv = 0.15 \text{ kg} \times 30 \text{ m/s} = 4.5 \text{ kg m/s}$.
Since it bounces back at the same speed, final momentum is $p_{f} = m(-v) = -4.5 \text{ kg m/s}$.
Change in momentum is $\Delta p = p_{f} – p_{i} = -4.5 – 4.5 = -9.0 \text{ kg m/s}$, so the magnitude is $9.0 \text{ kg m/s}$.
Force is defined as the rate of change of momentum: $F = \frac{\Delta p}{\Delta t}$.
Substituting the values, $F = \frac{9.0 \text{ kg m/s}}{1.0 \times 10^{-3} \text{ s}} = 9000 \text{ N}$.
Thus, Row D is the correct choice as it matches both calculated values.
▶️ Answer/Explanation
Detailed solution:
The resultant force $F$ acting on an object is defined as the rate of change of momentum.
First, calculate the change in momentum: $\Delta p = 15\,000 \text{ kg m/s} – 10\,000 \text{ kg m/s} = 5\,000 \text{ kg m/s}$.
Using the formula $F = \frac{\Delta p}{\Delta t}$, where $\Delta t = 8.0 \text{ s}$ is the time interval.
Substitute the values: $F = \frac{5\,000}{8.0} = 625 \text{ N}$.
Rounding to two significant figures, as given in the options, we get $630 \text{ N}$.
This matches Option A perfectly.
▶️ Answer/Explanation
Detailed solution:
Momentum is defined as the product of mass and velocity, $p = mv$, making statement D correct.
Impulse is defined as the product of force and the time interval, which equals the change in momentum, $F\Delta t = \Delta(mv)$, making statement B correct.
The principle of conservation of momentum states that total momentum remains constant in a closed system, making statement A correct.
Resultant force is actually the change in momentum per unit time, expressed as $F = \frac{\Delta p}{\Delta t}$.
Statement C incorrectly suggests force is the product of change in momentum and time ($F = \Delta p \times t$).
Therefore, statement C is the only incorrect statement in the list.