Final answer:
The impulse needed to stop the child is 200 Ns and the average force on the child is 4000 N. If the force were equal to the weight of an object, the mass of the object would be approximately 408.16 kg. Holding a child in your lap while riding in a car is not advisable due to the high forces exerted during a collision.
Step-by-step explanation:
To calculate the impulse needed to stop the child, we can use the formula:
Impulse = mass × change in velocity
The mass of the child is given as 20 kg and the change in velocity is the same as that of the car, which is 10 m/s. So, the impulse needed to stop the child is:
Impulse = 20 kg × 10 m/s = 200 Ns
To find the average force on the child, we can use the formula:
Average force = impulse / time
The time taken for the car to stop is given as 0.05 seconds. So, the average force on the child is:
Average force = 200 Ns / 0.05 s = 4000 N
If the force were equal to the weight of an object, we can use the formula:
Force = mass × acceleration due to gravity
Assuming the acceleration due to gravity to be approximately 9.8 m/s², we can find the mass of the object:
4000 N = mass × 9.8 m/s²
Mass = 4000 N / 9.8 m/s² ≈ 408.16 kg
To determine if you can lift that much mass, you may consider the weight of a textbook, which is about 1 kg. If you can lift a stack of ten textbooks, which would be 10 kg, then you are likely unable to lift the mass of 408.16 kg with ease.
Based on this calculation, it is evident that holding a child in your lap while riding in a car is not advisable. The force exerted on the child during a collision can be significantly higher than their weight, which can lead to severe injuries or even fatalities.