Hand tools energy sources

Tools and machines are a major source of injuries. Hand tools cause about 8% of lost-time occupational accidents machines cause an even greater share. Because powered tools and machines involve high levels of energy and power, injuries are often more severe than for hand-operated ones. 

From the beginning of recorded history, weeds have limited man s food supply and have imposed a heavy labor burden. Nearly all of early man s time was no doubt spent in obtaining food. Natural food sources permitted man s survival, even though periods of starvation must have been common. From 10,000 B.C. to 6,000 B.C., man began to cultivate crops by primitive methods (Fig. 1) (JL). About 6,000 B.C., he fashioned hand-weeding tools. Around 1,000 B.C., animal-powered implements were introduced. Prior to this time, human energy was the sole source available for weed control. 

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