Physics Review Question
Unit: Magnetism
Year: 1995 Question#: 7
Question: Which combination of concurrent forces could
not produce equilibrium?
(1 ) 10.N, 20.N, 50.N
(2 ) 20.N, 30.N, 50.N
(3 ) 30.N, 40.N, 50.N
(4 ) 40.N, 40.N, 50.N
What is this question really asking?
Explanation by: Chad H (partially)
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Answer 1
10.N, 20.N, 50.N
Correct
The least it could be is 10N (20N-10N). The most it could be is 30N (10N+20N).
It is not enough to be 50N. Equilibrium is something at a balanced state
where forces cancel others out to have it equal zero. With this combination
it can not be zero. return to top
Answer 2
20.N, 30.N, 50.N
Incorrect
This combination of vectors could reach equilibrium because any combination
of two vectors could create a range where the third vector would fit within
the range.
The combination of two vectors could be as large as the sum and as small
as the difference. For example, the 20N vector and the 30N vector could
produce any vector between 50N (20N + 30N) and 10N (30N - 20N) so the remaining
vector, 50N could be cancelled out by the other two.
return to top
Answer 3
30.N, 40.N, 50.N
Incorrect
This combination of vectors could reach equilibrium because any combination
of two vectors could create a range where the third vector would fit within
the range.
The combination of two vectors could be as large as the sum and as small
as the difference. For example, the 30N vector and the 40N vector could
produce any vector between 70N (30N + 40N) and 10N (40N - 30N) so the remaining
vector, 50N could be cancelled out by the other two. return
to top
Answer 4
40.N, 40.N, 50.N
This combination of vectors could reach equilibrium because any combination
of two vectors could create a range where the third vector would fit within
the range.
The combination of two vectors could be as large as the sum and as small
as the difference. For example, the 40N vector and the 40N vector could
produce any vector between 80N (40N + 40N) and 0N (40N - 40N) so the remaining
vector, 50N could be cancelled out by the other two. return
to top
What's this question really asking
Of these combinations, what ones could not make the object in a
state of balance?
return to top