forces and the laws of motion

A single force acting on an object is represented in a free-body diagram of the object by the following force vector: ↑. Which of the following force vectors represents a single force acting on the object that will bring the object into equilibrium?

(Arrow down)

The gravitational force exerted on an object would most likely be represented by which force vector?

(Arrow down)

A single force acts on an object. The components of this force act along the +x-axis and the -y-axis. The single force that will bring the object into equilibrium has components that act along the

-x-axis and +y-axis.

An object is at rest on an incline. The component of gravity acting downward and along the incline on the object is described as F= +8.0 N. Which axis is pointing up the incline?

-х-ахis

Sequence the steps in drawing a free-body diagram.

1. Identify the forces acting on the body and the direction of the forces. 2. Draw a diagram to represent the isolated object. 3. Draw and label force vectors for all the external forces acting on the object.

In the free-body diagram shown to the right, which of the following is the gravitational force acting on the car?

14 700 N

Why is force not a scalar quantity?

15. A scalar quantity has only magnitude. Force has both magnitude and direction; so, it cannot be a scalar quantity.

Two books are lying next to each other on a library table. The force due to gravity on the first book is 9 N and on the second is 13 N., The gravitational force on the table itself is 125 N. The floor supports the table with an upward force of 147 N. In a free-body diagram of the table, how many contact forces and how many field forces should be represented?

3, 1

In the free-body diagram shown to the right, which of the following is the gravitational force acting on the balloon?

4050 N

There are six books in a stack, and each book weighs 5 N. The coefficient of static friction between the books is 0.2. With what horizontal force must one push to start sliding the top five books off the bottom one?

5 N

A late traveler rushes to catch a plane, pulling a suitcase with a force directed 30.0° above the horizontal. If the horizontal component of the force on the suitcase is 60.6 N, what is the force exerted on the handle?

70.0 N

A sled weighing 1.0 x 10' N is held in place on a frictionless 20.0° slope by a rope attached to a stake at the top. The rope is parallel to the slope. What is the normal force of the slope acting on the sled?

94 N

21.Why is air resistance considered a form of friction?

Air resistance is a form of friction because it is a retarding force. It acts in the direction opposite an object's motion.

State Newton's first law of motion.

An object in motion will stay in motion and an object at rest will stay at rest unless acted on by an external force

Describe how applying the brakes to stop a bicycle is an example of force.

Force causes an acceleration or a change in an object's velocity. Applying the brakes decelerates the bicycle (accelerates it in the negative direction) and causes a change in the bicycle's velocity because the bicycle slows down.

18.Describe the forces acting on a car as it moves along a level highway in still air at a constant speed.

Gravity exerts a downward force on the car that is balanced by the normal force of the road acting upward on the car. The car's forward motion is opposed by the friction between the road and the tires and by the resistance of the air. The sum of these opposing forces is balanced by an equal and opposite force exerted by the engine and applied to the tires, where the road exerts a reaction force that is directed forward.

Which of the following statements describe free-body diagrams? I. Force diagrams show force vectors as arrows. II. Forces exerted on the object are represented. III. Forces exerted by the object are represented.

I and II

I. Force diagrams show force vectors as arrows. II. Forces exerted on the object are represented. III. Forces exerted by the object are represented.

I, II, and III

Which of the following statements are true about the concept of field forces?

I, II, and III

Which of the following statements describe an object in equilibrium?

I, II, and III

What happens to air resistance when an object accelerates?

It increases with increasing speed

Which of the following is true of inertia?

It is described in Newton's first law of motion..

19.Distinguish between mass and weight.

Mass is the amount of matter in an object and is an inherent property of an object. Weight is not an inherent property of an object and is the magnitude of the force due to gravity acting on the object.

When a car is moving, what happens to the velocity and acceleration of the car if the air resistance becomes equal to the force acting in the opposite direction?

The acceleration is then zero, and the car moves at a constant speed.

Which statement about the acceleration of an object is correct?

The acceleration of an object is directly proportional to the net external force acting on the object and inversely proportional to the mass of the object.

What are the units of the coefficient of friction?

The coefficient of friction has no units.

A hammer drives a nail into a piece of wood. Identify an action-reaction pair in this situation.

The hammer exerts a force on the nail; the nail exerts a force on the hammer

What is the natural tendency of an object that is in motion?

The natural condition for a moving object is to remain in motion once it has been set in motion.

While sitting in a lounge chair with the back inclined at an angle of 10° from the vertical, you tuck a pillow between your head and the chair. Then you lower the chair back to 40° and doze with the pillow in place. How has the net force on the pillow changed?

The net firvw has not changed becuase the pillow is still at rest

A small force acting on a human-sized object causes

a small acceleration

A force unit is defined as the product of a mass unit and a unit of

acceleration.

Which are simultaneous equal but opposite forces resulting from the interaction of two objects?

action-reaction pairs

Which of the following situations describes inertia?

all of the above

If a nonzero net force is acting on an object, then the object is definitely

being accelerated

Two forces act on an object. The magnitude of the net force acting on the object

cannot be determined from the given information.

A force of 5 N and a force of 15 N acting on an object can produce the following net forces except

d. 5 N.

Which of the following forces exists between objects even in the absence of direct physical contact?

field force

Which of the following is the cause of an acceleration?

force

An action exerted on an object which may change the object's state of rest or motion defines

force.

Units that measure weight are units of

force.

A free-body diagram represents all of the following except

forces exerted by the object

In a free-body diagram of an object, why are forces exerted by the object not included in the diagram?

forces exerted by the object do not change its motion

What causes a moving object to change direction?

forçe

Which of the following forces is an example of a contact force?

frictional force

Which of the following forces is an example of a field force?

gravitational force

As a basketball player starts to jump for a rebound, the player begins to move upward faster and faster until his shoes leave the floor. At the moment the player begins to jump, the force of the floor on the shoes is

greater than the player's weight

Which of the following is the tendency of an object to maintain its state of motion?

inertia

In the equation form of Newton's second law, EF = ma, what does F represent?

it is the vector sum of the external forces acting on the object

A newton is equivalent to which of the following quantities?

kg•m/s^2

The length of a force vector represents the

magnitude of the force

A measure of the quantity of matter is

mass.

A crate is released on a frictionless plank inclined at angle 0 with respect to the horizontal. Which of the following relationships is true? (Assume that the x-axis is parallel to the surface of the incline.)

none of the above

Two dogs are tugging on a toy. One dog pulls with a horizontal force of 14 N due north. The other is pulling due east with a horizontal force of 14 N. What is the direction of the net external horizontal force on the toy?

northeast

As an object falls toward Earth,

the upward acceleration of Earth is negligible because of its large mass.

In the equation form of Newton's second law, EF = ma, what does F represent?

the vector sum of the external forces acting on the object

Newton's third law of motion involves the interactions of

two objects and two forces.

A change in the gravitational force acting on an object will affect the object's

weight.

The magnitude of the gravitational force acting on an object is

weight.

A car goes forward along a level road at constant velocity. The additional force needed to bring the car into equilibrium is

zero.

In general, Fnet equals

ΣF