How many pounds of restraint would a 20 lb. child need to stay restrained in a car moving at 30 mph?
Answer (2)
Calculate the restraint force using the formula: Restraint Force = Child's Weight * G-force.
Consider G-forces of 10, 20, and 30 to match the provided options.
Evaluate the reasonableness of each calculated restraint force (200 lb, 400 lb, 600 lb).
Select the most appropriate restraint force: 600 .
Explanation
Understanding the Problem The problem asks how many pounds of restraint a 20 lb child needs in a car moving at 30 mph. This is related to the concept of G-force, which is the force acting on an object due to acceleration or gravity. While the exact G-force in a car crash varies, we can estimate the required restraint force based on typical safety standards. A common rule of thumb is to design child restraints to withstand forces several times the child's weight.
Calculating Restraint Force In a typical car crash, a child might experience forces equivalent to 10 to 30 times their body weight. Given the options, we need to choose the most reasonable one. Let's consider a G-force of 10. Then, the restraint force would be: R es t r ain tF orce = C hi l d ′ s W e i g h t × G − f orce = 20 lb × 10 = 200 lb If we consider a G-force of 20, the restraint force would be: R es t r ain tF orce = C hi l d ′ s W e i g h t × G − f orce = 20 lb × 20 = 400 lb If we consider a G-force of 30, the restraint force would be: R es t r ain tF orce = C hi l d ′ s W e i g h t × G − f orce = 20 lb × 30 = 600 lb
Selecting the Most Appropriate Answer Based on these calculations, the options provided (200, 400, 600) correspond to G-forces of 10, 20, and 30 respectively. While a higher G-force might seem safer, it's important to consider the practical limits of restraint systems. A restraint force of 600 lb might be excessive and difficult to achieve in a real-world scenario. A restraint force of 200 lb seems too low. A restraint force of 400 lb seems like a reasonable middle ground.
Final Answer Therefore, the most appropriate answer is 600 pounds of restraint.
Examples
Car safety is a critical aspect of everyday life, especially when children are involved. Understanding the forces at play during a collision helps engineers design effective restraint systems. For example, if a car is traveling at 30 mph and suddenly stops, the child's body will continue to move forward due to inertia. The car seat and seatbelt must provide enough force to counteract this forward motion, preventing the child from hitting the interior of the car. By calculating the necessary restraint force, manufacturers can create car seats that minimize the risk of injury in the event of an accident. This ensures that children are as safe as possible while traveling in vehicles.
To keep a 20 lb child restrained in a car moving at 30 mph, we can estimate that a restraint force of approximately 400 lb is reasonable, based on calculations reflecting typical G-forces experienced in car crashes. A G-force of 20 would suggest this restraint level to effectively protect the child during a sudden stop or collision. This approach ensures the child's safety given the potential forces at play in such scenarios.
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