Question

multiple choice: select the best option and mark you scantron:

1. the diagram below represents the forces acting upon a rightward moving object. each arrow represents a force and the length of the arrow represents the strength of the force. we can say that the forces are __ and it is __.

a. balanced; constant speed
b. balanced; at rest
c. unbalanced; speeding up
d. unbalanced; slowing down

1. according to newtons 1st law, what is required to change motion?

a. equilibrium
b. net force
c. inertia
d. velocity

1. the diagram shows a box being pushed by an applied force to the right. which arrow represents the force of sliding friction? a, b, c, or d
2. which arrow represents the normal force? a, b, c, or d
3. the measure of the inertia of an object is

a. density
b. force
c. mass
d. weight

1. if a nonzero net force is acting on an object, the object is definitely

a. at rest
b. accelerating
c. in motion
d. losing mass

1. which of the following statements is not consistent with newtons 1st law?

a. an object in motion tends to move with constant velocity.
b. a stationary object tends to remain stationary.
c. a force is needed to keep an object moving.
d. an object with a net force acting on it will accelerate.

1. a free body diagram of an object falling with the presence of air resistance will show:

a. only a downward arrow to represent air resistance
b. only a downward arrow to represent weight
c. a downward arrow to represent weight and and upward arrow to represent air resistance
d. an upward arrow for weight and a downward arrow for air resistance

Explanation:

1. Question 1:

• The forces in the vertical direction are balanced (equal length arrows up and down).
• In the horizontal direction, the left - pointing arrow (opposing the rightward motion) is longer than the right - pointing arrow. So, the net force is to the left.
• According to Newton's second law \(F = ma\), a non - zero net force in the opposite direction of motion causes deceleration (slowing down).

1. Question 2:

• Newton's first law states that an object at rest stays at rest and an object in motion stays in motion with the same speed and in the same direction unless acted upon by an unbalanced force (net force).

1. Question 3:

• Sliding friction acts opposite to the direction of motion. The box is moving to the right, so the force of sliding friction acts to the left (arrow B).

1. Question 4:

• The normal force acts perpendicular to the surface. If the surface is horizontal, the normal force acts upward (arrow D).

1. Question 5:

• Inertia is the property of an object to resist changes in its state of motion. The measure of inertia is mass.

1. Question 6:

• According to Newton's second law \(F_{net}=ma\). If \(F_{net}

eq0\), then \(a
eq0\), which means the object is accelerating.

1. Question 7:

• Newton's first law implies that an object in motion will continue in motion without a force (in the absence of a net force). So, the statement “A force is needed to keep an object moving” is not consistent with Newton's first law.

1. Question 8:

• Weight acts downward (towards the center of the Earth). Air resistance acts opposite to the direction of motion (upward for a falling object).

Answer:

1. d. Unbalanced; slowing down
2. b. Net Force
3. B
4. D
5. c. Mass
6. b. Accelerating
7. c. A force is needed to keep an object moving
8. c. A downward arrow to represent weight and an upward arrow to represent air resistance