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. The car experiences air resistance of 2 500 N. The force of friction exerted by the road on the tyres is 500 N. Draw a free-body diagram for this situation. A properly adjusted headrest can minimise or prevent whiplash, an injury on the neck and spine, resulting from the rapid forward acceleration in a rear-end collision. Name and define the property of a body that causes whiplash. A team of two athletes, A and B, are practising to compete in a canoe race. Athlete A has a mass of 60 kg, athlete B has a mass of 65 kg and the canoe a mass of 20 kg. Athlete A exerts an average force of 50 N and athlete B an average force of 55 N on the canoe using the paddles. During paddling, the magnitude of the water resistance on the canoe is 18 N. State Newton's Second Law in words. Calculate the acceleration of the canoe. When the canoe reaches a velocity of 3 m.s⁻¹, athlete B jumps off the canoe. Calculate the resultant force that is needed to increase the velocity of the canoe to 5 m.s⁻¹ in 6 seconds.

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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 - English General - NSC Technical Sciences - Question 2 - 2022 - Paper 1

Question 2

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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. The car experiences air resistance of 2 ... show full transcript

Worked Solution & Example Answer: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 - English General - NSC Technical Sciences - Question 2 - 2022 - Paper 1

Step 1

2.1 Draw a free-body diagram for this situation.

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Answer

To draw a free-body diagram, we first identify all the forces acting on the car:

Weight (W): The gravitational force pulling downwards, equal to the weight of the car, which is 10,000 N.
Normal Force (N): The upward force exerted by the road, which balances the weight of the car. This force also equals 10,000 N since the road is level.
Applied Force (F): The force exerted by the engine, acting eastwards, which is the force you need to represent in the diagram.
Air Resistance (F_air): Acting in the opposite direction (westwards), which is 2,500 N.
Friction Force (F_friction): Opposing the motion of the car, acting westwards, equal to 500 N.

The arrows should be labeled accordingly with their values and directions.

Step 2

2.2 Name and define the property of a body that causes whiplash.

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Answer

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.

Step 3

2.3.1 State Newton's Second Law in words.

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Answer

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.

Step 4

2.3.2 Calculate the acceleration of the canoe.

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Answer

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:

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

Step 5

2.3.3 Calculate the resultant force that is needed to increase the velocity of the canoe to 5 m.s⁻¹ in 6 seconds.

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Answer

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:

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

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 - English General - NSC Technical Sciences - Question 2 - 2022 - Paper 1

Worked Solution & Example Answer: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 - English General - NSC Technical Sciences - Question 2 - 2022 - Paper 1

2.1 Draw a free-body diagram for this situation.

2.2 Name and define the property of a body that causes whiplash.

2.3.1 State Newton's Second Law in words.

2.3.2 Calculate the acceleration of the canoe.

2.3.3 Calculate the resultant force that is needed to increase the velocity of the canoe to 5 m.s⁻¹ in 6 seconds.

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