Explain how car safety features like airbags and crumple zones reduce passenger injuries during a collision, referencing the impulse-momentum theorem and Newton's Third Law.

Car Safety Features

The safety features, such as airbags and crumple zones, contribute to passenger safety by increasing the time of impact during a collision. According to the impulse-momentum theorem ($F_{net} \Delta t = \Delta p$), for a given change in momentum ($\Delta p$), increasing the time interval ($\Delta t$) over which the momentum changes results in a decrease in the average net force ($F_{net}$) exerted on the passengers. A reduced force significantly lowers the risk and severity of injuries. Airbags also spread the impact force over a larger area of the body, further reducing pressure and potential harm.

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2008 Prelim Paper 1 Q6

6.1 The weight of truck A is the gravitational force exerted by the Earth on truck A. According to Newton's Third Law, the reaction force to the weight of truck A is the gravitational force exerted by truck A on the Earth.

Step 1: Calculate the magnitude of the weight of truck A.

$$W_A = m_A g$$ $$W_A = (2000 \text{ kg})(9.8 \text{ m/s}^2)$$ $$W_A = 19600 \text{ N}$$

The magnitude of the reaction force is equal to the magnitude of the weight.
The direction of the reaction force (force of truck A on Earth) is opposite to the direction of the weight (force of Earth on truck A).
The magnitude and direction of the 'reaction force' to the weight of truck A is $\boxed{\text{}19600 \text{ N UPWARDS}\text{}}$