Composition and resolution of forces and condition of equilibrium of forces - Advance Level

Composition and resolution of forces and condition of equilibrium of forces - Advance Level

Dear Readers,

Statics is the branch of mechanics that is concerned with the analysis of loads acting on physical systems that do not experience an acceleration, but rather, are in static equilibrium with their environment. .

Q1. The resultant of P and Q is R. If P is reversed, Q remaining the same, the resultant becomes R'. If R is perpendicular to R', then

•  2P=Q
•  P=Q
•  P=2Q
•  None of these

Solution
If R is perpendicular to R', then P=Q

Q2.A particle is acted upon by three forces P, Q and R. It cannot be in equilibrium, if P:Q:R =

•  1:3:5
•  3:5:7
•  5:7:9
•  7:9:11

Solution
It cannot be in equilibrium, if P:Q:R = 1:3:5

Q3.  Forces of 7 N, 5N and 3N acting on a particle are in equilibrium, the angle between the pair of forces 5 and 3 is

•  30
•  60
•  90
•  120

Solution
The angle between the pair of forces 5 and 3 is 60

Q4. The resultant of two forces P and Q is equal to √3Q and makes an angle of 30 with the direction of P, then P/Q =

•  1 or 2
•  3 or 5
•  3 or 4
•  4 or 5

Solution
P/Q = 1 or 2

Q5.Two men carry a weight of 240 Newton between them by means of two ropes fixed to the weight. One rope is inclined at 60 to the vertical and the other at 30 . The tensions in the ropes are

•  120N,120N
•  120N,120√3N
•  120√3N,120√3N
•  None of these

Solution
 The tensions in the ropes are 120N,120√3N

Q6. Three forces keep a particle in equilibrium. One acts towards west, another acts towards north-east and the third towards south. If the first be 5N, then other two are

•  6N,6N
•  5√2N,5N
• 5N,5N
•  None of these

Solution
If the first be 5N, then other two are 5√2N,5N

Q7.ABCD is a rigid square, on which forces 2, 3 and 5 kg. wt; act along AB, AD and CA respectively. Then the magnitude of the resultant correct to one decimal place in kg. wt. is

•  1
•  2
•  16
•  None of these

Solution
Then the magnitude of the resultant correct to one decimal place in kg. wt. is 16

Q8.If two forces P and Q act on such an angle that their resultant force R is equal to force P, then if P is doubled then the angle between new resultant force and Q will be

•  30
•  60
•  45
•  90

Solution
If P is doubled then the angle between new resultant force and Q will be 90

Q9.What will be that force when applying along any inclined plane will stop 10 kilogram weight, it is given that force, reaction of plane and weight of body are in arithmetic series

•  4 kilogram weight
•  6 kilogram weight
•  8 kilogram weight
•  7 kilogram weight

Solution
The force will be 6 kilogram weight

Q10. A bead of weight W can slide on a smooth circular wire in a vertical plane, the bead is attached by a light thread to the highest point of the wire, and in equilibrium the thread is taut. Then the tension of the thread and the reaction of the wire on the bead, if the length of the string is equal to the radius of the wire, are

•  W,2W
•  W,W
•  W,3W
•  None of these

Solution
Then the tension of the thread and the reaction of the wire on the bead, if the length of the string is equal to the radius of the wire, are W,W