Physics Exam 2 Gatch

the second at the doorknob

Two equal forces are applied to a door. The first force is applied at the midpoint of the door; the second force is applied at the doorknob. Both forces are applied perpendicular to the door. Which force exerts the greater torque?

Newton's third law

Two cars collide head-on. At every moment during the collision, the magnitude of the force the first car exerts on the second is exactly equal to the magnitude of the force the second car exerts on the first. This is an example of:

perpendicular to the plane

A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal force exerted by the plane on the block is directed:

The following forces act on the book: weight and normal force. Weight describes the interaction between the book and the Earth. Thus the "reaction" force is the Book pulling upward on the Earth. The normal force describes the interaction between the book and the table. Thus the "reaction" force is the book pushing down on the table (this is not the same as weight).

A book is resting on a table top. Identify all of the forces acting on the book. For each of these forces, identify the "reaction" force.

toward the curve's center

A car goes around a curve of radius r at a constant speed v. What is the direction of the net force on the car? A) toward the front of the car B) toward the back of the car C) toward the curve's center D) away from the curve's center

n < w

A car is rolling over the top of a hill at speed v. At this instant, A. n > w. B. n < w. C. n = w. D. We can't tell about n without knowing v.

constant acceleration

A constant net force acts on an object. Describe the motion of the object. A) constant velocity B) decreasing acceleration C) constant acceleration D) increasing acceleration

equal to the bucket's weight

A person is lowering a bucket into a well with a constant speed. The force exerted by the rope on the bucket is A) greater than the bucket's weight B) equal to the bucket's weight C) less than the bucket's weight D)zero

Fnet=0 and Torque net = 0

A rigid body is in equilibrium if

The car exerts the same amount of force on the truck as the truck exerts on the car.

A small car is pushing a larger truck that has a dead battery. The mass of the truck is larger than the mass of the car. Which of the following statements is true? 1. The car exerts a force on the truck but the truck doesn't exert a force on the car. 2. The car exerts a larger force on the truck than the truck exerts on the car. 3. The car exerts the same amount of force on the truck as the truck exerts on the car. 4. The truck exerts a larger force on the car than the car exerts on the truck. 5. The truck exerts a force on the car but the car doesn't exert a force on the truck.

the friction force exerted by the ramp

A solid bowling ball rolls down a ramp. Which of the following forces exerts a torque on the bowling ball about its center?

tension

Along the string, away from the object (T)

the upward force that the apple exerts on the Earth

An apple sits at rest on a horizontal table top. The gravitational force on the apple (its weight) is one half of an action-reaction pair. What force is the other half?

weight

An example of a force that acts at a distance is:

Newton's First Law

An object at rest tends to stay at rest and objects in motion tend to stay in motion. (until acted upon by an external force)

The net force on the object is zero

An object is moving with a constant velocity. Which of the following statements is true? A) There are no forces acting on the object B) The net force on the object is zero C) A constant force is being applied in the direction of motion D) A constant force is being applied to the direction of opposite motion

Newton's Third Law

If object A exerts a force on object B, object B will exert a force of equal magnitude and opposite direction on object A

move with constant velocity

In the absence of an external force, a moving object will A) stop immediately B) slow down C) speed up D) move with constant velocity

μ k < μ s

It's more difficult to start moving a heavy carton than it is to keep pushing it with a constant velocity because:

frictional force

Parallel to the surface of contact, opposite of the (expected) motion (μN)

normal force

Perpendicular to the surface of contact, toward the object (N)

weight

Straight down, or toward the center of the Earth (mg)

The object will continue moving in a straight line will constant velocity. It will not speed up or slow down.

Suppose an object is moving in the absence of a net force. Describe the subsequent motion of the object.

The object will acceleration in the direction of the net force.

Suppose an object is moving in the presence of a constant net force. Describe the subsequent motion of the object.

Newton's Second Law

The vector sum of all forces acting on an object equals the object's mass times acceleration (rate of change of velocity)

is directed toward the center of the circular path

When an object experiences uniform circular motion, the direction of the net force is: A) in the same direction as the motion of the object B) in the opposite direction of the motion of the object C) is directed toward the center of the circular path D) is directed away from the center of the circular path

the Earth being pulled up

When you sit on a chair, the "reaction" to your weight is: A) the chair pushing on you B) the floor pushing up on the chair C) the Earth being pulled up D) the chair pushing down on the floor

A

You apply the same force on two objects. Object 1 has mass M and object 2 has mass 5M. The acceleration of object 2 is: A) one-fifth as that of object 1 B) ten times that of object 1 C) the same as that of object 1 D) five times that of object 1

A,B, and D, but not C

You've just kicked a rock, and it is now sliding across the ground about 2 meters in front of you. Which of these forces act on the ball? A. Gravity, acting downward B. The normal force, acting upward C. The force of the kick, acting in the direction of motion D. Friction, acting opposite the direction of motion E. A, B, and D but not C.