Question

1. Several forces act on an object at rest. It is known that the sum of the forces acting on the object is zero. Which statement is necessarily true?
A) The object will remain stationary.
B) The object's center of mass may move in such a way that the object will roll without slipping.
C) The object's center of mass will not move, but the object may begin to rotate.
D) The object's center of mass may accelerate and the object may begin to rotate.
E) The object's center of mass may accelerate, but the object will remain in the same orientation.

2. A heavy boy and a lightweight girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw?
A) It is impossible to say without knowing the masses.
B) It is impossible to say without knowing the distances.
C) The side the boy is sitting on will tilt downward.
D) Nothing, the seesaw will still be balanced.
E) The side the girl is sitting on will tilt downward.

3. A cone balanced on its small end is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
E) negative equilibrium.

4. A sphere hanging freely from a cord is in
A) stable equilibrium.
B) unstable equilibrium.
C) neutral equilibrium.
D) positive equilibrium.
E) negative equilibrium.

5. The region from the origin to the elastic limit on an applied force versus elongation graph for a typical metal under tension is referred to as the
A) elastic region.
B) proportional region.
C) plastic region.
D) ultimate strength region.
E) breaking region.

6. The maximum elongation of a typical metal is reached at the
A) proportional limit.
B) elastic limit.
C) inelastic limit.
D) breaking point.
E) ultimate strength.

7. Strain is
A) the ratio of the change in length to the original length.
B) the stress per unit area.
C) the same as force.
D) the applied force per cross-sectional area.
E) the ratio of stress to elastic modulus.

Answer 1

1. Several forces act on an object at rest. It is known that the sum of the forces acting on the object is zero. Which statement is necessarily true

It means net force is zero, However, torque is not zero.  

correct option - The object's center of mass will not move, but the object may begin to rotate

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2)

A heavy boy and a lightweight girl are balanced on a massless seesaw. If they both move forward so that they are one-half their original distance from the pivot point, what will happen to the seesaw

as they have moved same distance, it is as if the see saw has shortened

correct option - Nothing will happen; the seesaw will still be balanced

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3. A cone balanced on its small end is in

correct option - unstable equilibrium

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4. A sphere hanging freely from a cord is in

correct option - stable equilibrium

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5. The region from the origin to the elastic limit on an applied force versus elongation graph for a typical metal under tension is referred to as the

not sure, but I think its elastic limit.

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6. The maximum elongation of a typical metal is reached at the

correct option - Breaking point

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7. Strain is

correct option - the ratio of the change in length to the original length