The 2.5-kg head of an ax exerts a force of 80 kN as it penetrates 18 mm into the truck of a tree. The speed of the ax head when it strikes the tree is

Question

BlackTom AI · Accepted Answer

To tackle this problem, I’ll apply the work-energy principle, assuming the braking (stopping) force is constant as the ax head penetrates the wood.
First, write the work done by the stopping force equal to the initial kinetic energy: F · d = 0.5 · m · v^2.
Given values: mass m = 2.5 kg, stopping force F = 80 kN = 80{,}000 N, and penetration distance d = 18 mm = 0.018 m.
Compute 2 F d: 2 × 80{,}000 × 0.018 = 2880.
Now divide by the mass: (2 F d) / m = 2880 / 2.5 = 1152.
Take the square root to find the speed: v = sqrt(1152) ≈ 33.94 m/s ≈ 34 m/s.
Option-by-option reasoning:
- 1. 1.2 m/s: This value is far too small; even with a tiny stopping distance or a much larger mass, the result would not drop by nearly an order of magnitude. The calculation above shows a speed around 34 m/s, so 1.2 m/s is not plausible here.
- 2. 107 m/s: This is too large given the same energy balance. To reach 107 m/s would require a much smaller work done (smaller F or d) or a much smaller m; neither condition holds with the provided numbers, so this overestimates the initial speed.
- 3. 34 m/s: This matches the computed value from the energy balance with the given force and distance. It aligns with the formula v = sqrt(2 F d / m) and the provided data.
- 4. 3.4 m/s: This is exactly an order-of-magnitude lower than the correct result and would result from an incorrect halving or misplacement of decimal points in the energy terms; it does not satisfy the energy equation with the given F, d, and m.
In summary, applying the work-energy relation with the stated force and penetration distance yields a velocity of about 34 m/s, which corresponds to option 3.

The 2.5-kg head of an ax exerts a force of 80 kN as it penetrates 18 mm into the truck of a tree. The speed of the ax head when it strikes the tree is 单项选择题

类似问题

A joule (J) is the unit of measure of

Find the work done on a box if it is pushed with a horizontal force of 1.5 N for a distance of 1.2 m. Give your answer to two decimal places.

A frictional force of 5 N west acts on a trolley as it rolls 3.4 m to the east. How much work did the frictional force do on the trolley? Give your answer to the nearest whole number.

A 0.20 kg clockwork toy car, starting from rest, travels 16 cm in 0.21 s with a constant acceleration. How much work is done on it? Give your answer to two significant figures.

How much work input is required to lower (not drop) a 120 pound weight from the top of a 3 foot table to the floor?

What is the relative efficiency of W with respect to X?

更多留学生实用工具

智能学习助手

风格化写作助手

论文查重助手

文献引用助手

课堂转译助手

课堂笔记助手

Quiz搜索助手

学校历年真题

智能刷题助手

智能匹配练习

希望你的学习变得更简单