Physics Chapter 2

Your weight is (A) the gravitational attraction between you and the Earth. (B) actually your mass. (C) a property of mechanical equilibrium. (D) all of the above (E) none of the above

A

One-half second after starting from rest, a freely falling object will have a speed of about (A) 2.5 m/s. (B) 10 m/s. (C) 5 m/s. (D) 20 m/s. (E) none of the above

C

Someone standing at the edge of a cliff throws one ball straight up and another ball straight down at the same initial speed. Neglecting air resistance, the ball to hit the ground below the cliff with the greatest speed will be the one initially thrown (A) upward. (B) downward. (C) They will both hit with the same speed.

C

The gain in speed each second for a freely falling object is about (A) 20 m/s. (B) 0 m/s. (C) 10 m/s. (D) 5 m/s. (E) depends on the initial speed

C

What equation shows the relationship among speed, distance, and time? (A) Speed = distance covered⋅ travel time (B) Speed = travel time/distance covered (C) Speed = distance covered / travel time

C

What is the name of the property of objects to maintain their states of motion? (A) Weight (B) Acceleration (C) Inertia (D) Velocity

C

When a 10-N object is suspended at rest by a vertical strand of rope, the tension in the rope is (A) more than 10 N. (B) zero. (C) 10 N. (D) less than 10 N.

C

Where would your mass be greater − on Earth or on the Moon? (A) Your mass would be greater on the Moon because of its weaker force of gravity. (B) Your mass would be greater on Earth because of its stronger force of gravity. (C) Mass is the same everywhere.

C

Why do we say that velocity is a vector and speed is not a vector? (A) Velocity involves only magnitude. Speed involves only direction. (B) Velocity involves only direction. Speed involves only magnitude. (C) Velocity involves both magnitude and direction. Speed involves only magnitude. (D) Velocity involves only magnitude. Speed involves both magnitude and direction.

C

Which has the greatest density? (A) 1 kg of feathers (B) 1 kg of lead (C) 10 kg of feathers

B

A ball is rolling down an Inclined Plane. How does the distance traveled by the ball in the second half second compare with the distance traveled by the ball in the first half second? (A) It increases (B) It decreases (C) It stays the same

A

A freely falling object has a speed of 40 m/s at one instant. Exactly one second later its speed will be. (A) 50 m/s (B) the same (C) 10 m/s (D) 45 m/s

A

A man weighing 800 N stands at rest on two bathroom scales so that his weight is distributed evenly over both scales. The reading on each scale is (A) 400 N. (B) 800 N. (C) 1600 N. (D) 200 N. (E) none of the above

A

A man weighing 800 N stands at rest on two bathroom scales so that one scale shows a reading of 500 N. The reading on the other scale is (A) 300 N. (B) 800 N. (C) 400 N. (D) 200 N.

A

A motorcycle undergoes acceleration when it (A) changes speed or direction. (B) gains speed only. (C) changes direction only. (D) decreases speed only.

A

An object in mechanical equilibrium is an object (A) at rest or moving with constant velocity. (B) only moving at constant velocity. (C) only at rest. (D) only without motion.

A

An object is pulled northward with a force of 10 N and southward with a force of 15 N. The magnitude of the net force on the object is (A) 5 N. (B) 0 N. (C) 15 N. (D) 10 N. (E) none of the above

A

Did Aristotle believe that forces are necessary to keep moving objects moving, or did he believe that, once moving, they would move by themselves? (A) Aristotle believed that forces are necessary to keep objects moving. (B) Aristotle believed that moving objects would move by themselves.

A

Does the speedometer on a vehicle show the average speed or the instantaneous speed? (A) The speedometer shows instantaneous speed. (B) The speedometer shows average speed.

A

Neglecting air resistance, when you toss a rock upward, by about how much does its upward speed decrease each second? (A) 10 m/s (B) 10 m/s2 (C) The answer depends on the initial speed

A

Suppose you push on a heavy crate, but not hard enough to make it slide. Does a friction force act on the crate? (A) Yes, opposite to your push, just enough so that ∑ F = 0. (B) No, the friction force doesn't act.

A

Suppose you push on a heavy crate, but not hard enough to make it slide. Does a friction force act on the crate? (A) Yes, opposite to your push, just enough so that ⅀F =0 (B) No, the friction force doesn`t act

A

The average speed of a horse that gallops a distance of 10 km in a time of 30 min is (A) 20 km/h. (B) more than 30 km/h. (C) 10 km/h. (D) 30 km/h.

A

The force of friction on a sliding object is 10 N. The applied force needed to maintain a constant velocity is (A) 10 N. (B) less than 10 N. (C) more than 10 N.

A

The vertical height attained by a basketball player who achieves a hang time of a full 1 s is about (A) 1.2 m. (B) 0.8 m. (C) 2.5 m. (D) 1 m. (E) more than 2.5 m.

A

What does ⅀F = 0 mean? (A) The vector sum of all the forces that act on an object equals zero> The forces cancel! (B) Every force that act on an object equals zero. The forces cancel!

A

What equation shows the relationship among velocity, time, and acceleration? (A) Acceleration = change in velocity / time interval (B) Acceleration =time interval / change in velocity (C) Acceleration = change in velocity ⋅ time interval

A

When Galileo rolled a ball down an incline and up another incline, he found that the ball rolled nearly to (A) its initial height. (B) halfway its original height. (B) a point higher than its original height. (C) three quarters its original height.

A

When you weigh yourself, how does the support force of the scale acting on you compare with the gravitational force between you and Earth? (A) The support force is equal to the gravitational force and has the opposite direction. (B) The support force is greater than the gravitational force and acts at right angle to it. (C) The support force is equal to the gravitational force and has the same direction. (D) The support force is less than the gravitational force and has the same direction.

A

Whenever the net force on an object is zero, its acceleration (A) is zero. (B) may be zero.

A

Where would your weight be greater − on Earth or on the Moon? (A) Your weight would be greater on Earth because of its stronger force of gravity. (B) Your weight would be greater on the Moon because of its weaker force of gravity. (C) Weight is the same everywhere.

A

A bullet is dropped into a river from a very high bridge. At the same time, another bullet is fired from a gun, straight down towards the water. Neglecting air resistance, the acceleration just before striking the water (A) is greater for the dropped bullet. (B) is the same for each bullet. (C) depends on how high they started. (D) is greater for the fired bullet. (E) none of the above

B

A kilogram is a measure of an object's (A) gravity. (B) mass. (C) force. (D) center of mass. (E) weight.

B

Compared with the mass of a certain object on Earth, the mass of the same object on the Moon is (A) less. (B) the same. (C) more.

B

Hang from a pair of gym rings and the upward support forces of the rings will always (A) each be half your weight. (B) add up to equal your weight. (C) each be equal to your weight.

B

How does the direction of a friction force compare with the direction of motion of a sliding object? (A) The direction of friction is perpendicular to the direction of motion. (B) The direction of friction is opposite to the direction of motion. (C) The direction of friction is the same as the direction of motion.

B

If a freely falling object were somehow equipped with a speedometer, its speed reading would increase each second by about (A) 15 m/s. (B) 10 m/s. (C) 5 m/s. (D) a variable amount (E) depends on its initial speed

B

If a freely falling object were somehow equipped with an odometer to measure the distance it travels, then the amount of distance it travels each succeeding second would be (A) constant. (B) greater than the second before. (C) less and less.

B

One kg weighs 10 N on Earth. Would it weigh more or less on the Moon? (A) One kg would weigh more on the Moon. (B) One kg would weigh less on the Moon.

B

Suppose a jumper claims a hang time of 2 s. Then that jumper must be able to jump a height of (A) 1 m. (B) 5 m. (C) 4 m. (D) 2 m. (E) 3 m.

B

Ten seconds after starting from rest, a freely falling object on Earth will have a speed of about (A) more than 100 m/s. (B) 100 m/s. (C) 10 m/s. (D) 50 m/s.

B

The scientist to first introduce the concept of inertia was (A) Copernicus. (B) Galileo. (C) Newton. (D) Aristotle.

B

When you toss a ball upward, by how much does its upward speed decrease each second? (A) The speed decreases by 5 m/s each second. (B) The speed decreases by 10 m/s each second. (C) The speed decreases by 15 m/s each second. (D) The speed decreases by 20 m/s each second.

B

Whereas Aristotle relied on logic in explaining nature, Galileo relied on (A) observation. (B) experiment. (C) patterns. (D) mathematics.

B

Which depends on gravity − weight or mass? (A) Mass depends on gravity. (B) Weight depends on gravity. (C) Both weight and mass depend on gravity.

B

Which dominated Galileo's way of extending knowledge − philosophical discussion or experiment? (A) Philosophical discussion. (B) Experiment.

B

Which has the greater density − 1 kg of water or 10 kg of water? (A) 1 kg of water. (B) Neither, since any amount of water has the same density. (C) 10 kg of water.

B

Which has the greater mass? (A) a king-size pillow (B) an automobile battery (C) both about the same

B

Why does the unit of time appear twice in the definition of acceleration? (A) The unit of time appears once for the unit of distance, and again for the time interval. (B) The unit of time appears once for the unit of velocity, and again for the time during which the velocity changes. (C) The unit of time appears once for the unit of velocity, and again for the total distance covered. (D) The unit of time appears once for the unit of force, and again for the time interval during which the force changes.

B

A ball is thrown 125 m upward and then falls the same distance back to the Earth. Neglecting air resistance, its total time in the air is about (A) 5 s. (B) 15 s. (C) 10 s. (D) more than 20 s.

C

A car accelerates from rest at 2 m/s2. What is its speed 3 s after the car starts moving? (A) 2 m/s (B) 3 m/s (C) 6 m/s (D) 4 m/s (E) none of the above

C

A pot falls from a ledge and hits the ground 45 m below. The speed with which it hits the ground is about (A) 120 m/s. (B) 60 m/s. (C) 30 m/s. (D) more than 120 m/s.

C

An object is in free fall. At one instant, it travels at a speed of 50 m/s. Exactly 1 s later, its speed is about (A) 100 m/s. (B) 55 m/s. (C) 60 m/s. (D) 25 m/s. (E) 50 m/s.

C

Drop a rock from a 5-m height and it accelerates at 10 m/s2 and strikes the ground 1 s later. Drop the same rock from a height of 2.5 m and its acceleration of fall is (A) twice as much. (B) about half. (C) the same.

C

If a baseball being thrown goes from zero to 30 m/s in 0.1 s, what is its average acceleration? (A) 3000 m/s2 (B) 3 m/s2 (C) 300 m/s2 (D) 30 m/s2 (E) none of the above

C

If we push a crate at constant velocity, how does friction acting on the crate compare with our pushing force? The pushing force and the surface are horizontal. (A) The friction force acting on the crate is less than the pushing force and has the same direction. (B) The friction force acting on the crate is greater than the pushing force and has the opposite direction. (C) The friction force acting on the crate is equal to the pushing force and has the opposite direction. (D) The friction force acting on the crate is equal to the pushing force and has the same direction.

C

A 1-kg mass at Earth's surface weighs about (A) 1 N. (B) 12 N. (C) 5 N. (D) 10 N. (E) none of the above

D

An apple falls from a tree and hits the ground 5 m below. It hits the ground with a speed of about (A) 15 m/s. (B) 5 m/s. (C) 20 m/s. (D) 10 m/s. (E) not enough information given to estimate

D

An object is pulled with two forces: 5 N North and 10 N South. The magnitude of the net force is (A) 0 N. (B) 15 N. (C) 10 N. (D) 5 N.

D

An object that has twice as much mass as another object also has twice as much (A) velocity. (B) volume. (C) gravitational acceleration. (D) inertia.

D

Density is the ratio of (A) weight to mass. (B) weight to volume. (C) mass to weight. (D) mass to volume.

D

If a car increases its velocity from zero to 60 km/h in 10 s, its acceleration is (A) 10 km/h×s (B) 600 km/h×s (C) 3 km/h×s (D) 6 km/h×s (E) 60 km/h×s

D

If you push on a heavy crate to the right and it slides, what is the direction of friction on the crate? (A) Downward (B) Upward (C) To the right (D) To the left

D

One object has twice as much mass as another object, and also has twice as much (A) gravitational acceleration. (B) volume. (C) velocity. (D) inertia. (E) all of the above

D

The hang time of professional basketball players is typically (A) more than 1 s. (B) more than 2 s. (C) 1 s. (D) less than 1 s.

D

The two measurements necessary for calculating average speed are (A) acceleration and time. (B) distance and acceleration. (C) velocity and time. (D) distance and time. (E) velocity and distance.

D

Which direction does a table push a book resting on it? (A) Left. (B) Right. (C) Down. (D) Up.

D

Which has zero acceleration? An object (A) at rest. (B) moving at constant velocity. (C) in mechanical equilibrium. (D) all of the above (E) none of the above

D

Disregarding air drag, how fast must you toss a ball straight upward in order for the ball to remain in the air for a total time of 2 s? (A) 20 m/s (B) 15 m/s (C) 5 m/s (D) 7.5 m/s (E) 10 m/s

E