f4 physical

Larry

2010-01-11 5:01 am

An object is acted on by three forces F1,F2 and F3 in suitable directions such
that it remains at rest .Which of the following combinations of the magnitude of
the foces is / are possible ????

(1) F1=3N F2=4N F3=5N
(2) F1=3N F2=4N F3=7N
(3) F1=3N F2=5N F3=9N

can choose more than one

回答 (1)

天同

2010-01-11 5:24 am

✔ 最佳答案

Statements (1) and (2) are possible.
In equilibrium, the three forces can form the three sides of a triangle (Principle of Triangle of Forces). In geometry, we know that the sum of any two sides of a triangle must be longer than the third.

Hence, statement (1) is correct because the three force vectors can form a right angle triagle with the 5 N force as the hypotenus.

Statement (2) is correct because the magnitudes of (F1 + F2) = F3. If F1 and F2 are in the same direction, and F3 in opposite direction, they can balance one another.

Statement (3) is wrong simply because the three forces cannot form the three sides of a triangle sucessfully, since the magnitudes of (F1+F2) < F3

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