A car with a weight of 10 000 N is travelling eastwards on a level road, while the engine is applying a force, F, eastwards - NSC Technical Sciences - Question 2 - 2022 - Paper 1

The property of a body that causes whiplash is known as inertia. Inertia is defined as the tendency of an object to resist changes in its state of motion. This means that when a vehicle suddenly stops, the occupants continue moving forward due to their inertia. If the headrest is not properly adjusted, this can lead to rapid forward acceleration of the head, resulting in whiplash injuries.

Newton's Second Law states that the acceleration of an object is directly proportional to the net force acting on it and inversely proportional to its mass. In equation form, this can be represented as:

$F_{net} = ma$

where $F_{net}$ is the net force applied, $m$ is the mass of the object, and $a$ is the acceleration produced.

To calculate the acceleration, we first need to determine the net force acting on the canoe. The total force exerted by the athletes is:

$F_{total} = F_A + F_B - F_{water resistance}$ Where:

• Force exerted by athlete A, $F_A = 50 N$
• Force exerted by athlete B, $F_B = 55 N$
• Magnitude of water resistance, $F_{water resistance} = 18 N$

Calculating:

$F_{total} = 50 N + 55 N - 18 N = 87 N$

Now we apply Newton's Second Law:

$a = \frac{F_{net}}{m}$

The total mass is:

$m = 60 kg (A) + 65 kg (B) + 20 kg (canoe) = 145 kg$

Thus the acceleration is:

$a = \frac{87 N}{145 kg} \approx 0.60 m.s^{-2}$

To calculate the resultant force needed, we first find the required acceleration. Using the formula:

$a = \frac{\Delta v}{\Delta t}$

where

• $\Delta v$ is the change in velocity
• $\Delta t$ is the time interval.

The initial velocity ($v_i$) is 3 m.s⁻¹, and the final velocity ($v_f$) is 5 m.s⁻¹, so:

$\Delta v = v_f - v_i = 5 m.s^{-1} - 3 m.s^{-1} = 2 m.s^{-1}$

Substituting into the formula gives:

$a = \frac{2 m.s^{-1}}{6 s} \approx 0.33 m.s^{-2}$

Now, to find the net force needed, we apply Newton's Second Law again:

$F_{net} = ma$

The total mass remains 145 kg, so:

$F_{net} = 145 kg * 0.33 m.s^{-2} \approx 48 N$