Question
A wooden plank rests in equilibrium on two rocks on opposite sides of a narrow stream.
How are the sizes of the forces related?
A P + Q = R
B P + R = Q
C P = Q = R
D P = Q + R
Answer/Explanation
Ans: B
Question
A plane lamina with centre of mass X touches the ground at point P.
Which diagram shows the lamina in equilibrium?
Answer/Explanation
Ans: B
Question
The diagram shows sections of four objects of equal mass. The position of the centre of mass
of each object has been marked with a cross.
Which object is the most stable?
Answer/Explanation
Ans: A
Question
A see-saw is made by resting a long plank of wood with its centre of mass on a barrel.
A boy sits on one side of the barrel and a girl sits on the other side so that the see-saw is balanced.
Which statement must be true?
A boy’s weight = girl’s weight
B distance x = distance y
C total downward force = total moment about the barrel
D resultant force and resultant moment are both zero
Answer/Explanation
Ans: D