Employ the TOPS advantage: build fun stuff with simple things. Devise levers, pulleys, reinvent the wheel, check gear ratios, calculate horsepower, win a tug-of-war. Use spring scales to weigh loads, measure effort, and calculate efficiency. Discover that machines save effort, but never reduce work!
Ex library book
$20.00 Original price was: $20.00.$8.00Current price is: $8.00.
1 in stock