QuizBBB: January 2017

Archive for January 2017

A disco ball falls from the midpoint of the ceiling of a moving van. It lands

A) at a point in front of the midpoint
B) at a point behind the midpoint
C) directly below the midpoint

Answer: C

A package falls out of an airplane that is traveling at 300m/s. Neglecting air resistance, what is its horizontal velocity before hitting the ground?

A) greater than 300m/s
A package falls out of an airplane that is traveling at 300m/s. Neglecting air resistance, what is its horizontal velocity before hitting the ground?
A) greater than 300m/s
B) equal to 300m/s
C) less than 300m/s

Answer: C

What is the acceleration of a freely falling object

A) 10m/s^2
B) 0m/s^2
C) 5m/s^2

Answer: A

When you yank a table cloth out from under your dishes you are demonstrating

A) impulse
B) inertia
C) gravity
D) momentum

Answer: B

As an object falls

A) its velocity increases
B) its acceleration increases

Answer: A

A car traveling at 100 km/hr strikes an unfortunate bug and splatters it. The force of impact is

A) greater on the bug.
B) greater on the car.
C) the same for both.

Answer: C

A vehicle that weights 400 N on the surface of the Earth is traveling in outer space at a speed of 400 m/s . It can be stopped by applying a constant force of 20 N for

A) 2 seconds.
B) 4 seconds.
C) 80 seconds.
D) 400 seconds.
E) 800 seconds.

Answer: E

A horse exerts 500N of force on a heavy wagon. The wagon pulls back on the horse with an equal force. The wagon still accelerates because

A) these forces are not an action-reaction pair
B) nevertheless there is still an unbalance force on the wagon
C) the horse pulls on the wagon a brief time before the wagon reacts
D) the wagon doesn't accelerate because these forces are equal and opposite.

Answer: B

Joe pushes Bill, who is asleep. Bill

A) does not push even after he wakes up
B) pushes Joe equally hard even without waking up
C) will ineviable push Joe when he wakes up
D) push Joe immediately, but not as hard

Answer: B

Earth pulls on the moon. Similarly the moon pulls on Earth, evidence that

A) these two pulls comprise an action-reaction pair.
B) Earth is larger so its pull is larger.
C) the moon is smaller so its pull is smaller.
D) larger objects pull harder.

Answer: A

As a ball falls, the action force is the pull of Earth on the ball. The reaction force is the

A) air resistance acting against the ball.
B) acceleration of the ball.
C) pull of the ball's mass on the Earth.
D) none of these

Answer: C

A player catches a ball. Consider the action force to be the impact of the ball against the player's glove. The reaction to this force is the

A) player's grip on the glove.
B) force the glove exerts on the ball.
C) friction of the ground against the player's shoes.
D) muscular effort in the player's arms.
E) none of these

Answer: B

A large and a small person wish to parachute at equal terminal velocities. The larger person will have to

A) jump first from the plane.
B) get a larger parachute.
C) pull upward on the supporting strands to decrease the downward net force.
D) jump lightly.

Answer: B

A skydiver's terminal velocity will be greatest if she falls

A) head first.
B) lying flat on her back.
C) lying flat on her stomach.
D) with her parachute open.

Answer: A

A skydiver jumps from a high-flying plane. As her velocity of fall increases, her acceleration

A) increases.
B) decreases.
C) remains unchanged regardless of air resistance.

Answer: B

When a falling object has reached its terminal velocity, its acceleration is

A) constant.
B) zero.
C) g.

Answer: B

A 2000-kg car experiences a braking force of 10,000 N and skids to a stop in 6 seconds. The speed of the car just before the brakes were applied was

A) 1.2 m/s.
B) 15 m/s.
C) 30 m/s.
D) 45 m/s.
E) none of these

Answer: C

A car traveling at 22 m/s comes to an abrupt halt in 0.1 second when it hits a tree. What is the deceleration in meters per second per second of the car?

A) 110
B) 220
C) 800
D) 880
E) can't be solved without the mass of the car

Answer: B

A jumbo jet has a mass of 100,000 kg. The thrust for each of its four engines is 50,000 N. What is the jet's acceleration in meters per second per second when taking off?

A) 0.25
B) 1
C) 2
D) 4
E) none of these

Answer: C

A rock is thrown vertically into the air. At the very top of its trajectory the net force on it is

A) less than its weight.
B) more than its weight.
C) equal to its weight.

Answer: C

Neglecting friction, a large block of ice and a small block of ice start sliding down an incline together. The heavier block will get to the bottom

A) before the light block.
B) after the light block.
C) at the same time as the light block.

Answer: C

An object following a straight-line path at constant speed

A) has a net force acting upon it in the direction of motion.
B) has zero acceleration.
C) has no forces acting on it.
D) none of these

Answer: B

The mass of a pet turtle that weighs 10 N is

A) about 1 kg.
B) about 10 kg.
C) about 100 kg.
D) about 1000 kg.
E) none of these

Answer: A

A girl pulls on a 10-kg wagon with a constant horizontal force of 30 N. If there are no other horizontal forces, what is the wagon's acceleration in meters per second per second?

A) 0.3
B) 3.0
C) 10
D) 30
E) 300

Answer: B

An apple at rest weighs 1 N. The net force on the apple when it is in free fall is

A) 0 N.
B) 0.1 N.
C) 1 N.
D) 9.8 N.
E) none of these

Answer: C

A 10-N falling object encounters 4 N of air resistance. The net force on the object is

A) 0 N.
B) 4 N.
C) 6 N.
D) 10 N.
E) none of these

Answer: C

The force of friction on a sliding object is 10 newtons. The applied force needed to maintain a constant velocity is

A) more than 10 N.
B) less than 10 N.
C) 10 N.

Answer: C

An object is propelled along a straight-line path by a force. If the net force were doubled, the object's acceleration would be

A) half as much.
B) the same.
C) twice as much.
D) four times as much.
E) none of these

Answer: C

The Newtone is a unit of

A) density
B) mass
C) inertia
D) force

Answer: D

Strange as it may seem, it is just as hard to accelerate a car on a level surface on the moon as it is here on the Earth. This is because

A) the mass of the car is independent of gravity.
B) the weight of the car is independent of gravity.
C) Nonsense! A car is much more easily accelerated on the moon than on the Earth.

Answer: A

If one object has twice as much mass as another object, it also has twice as much

A) inertia.
B) velocity.
C) acceleration due to gravity.
D) volume.
E) all of these

Answer: A

An object maintains a constant acceleration unless there is a change in

A) its mass
B) the air resistance
C) the applied force
D) any of the above

Answer: D

A ball is thrown upwards. Neglecting air resistance, what initial upward speed does the ball need to remain in the air for a total time of 10 seconds?

A) about 50 m/s
B) about 80 m/s
C) about 100 m/s
D) about 110 m/s

Answer: A

A bullet is dropped from the top of the Empire State Building while another bullet is fired downward from the same location. Neglecting air resistance, the acceleration of

A) the fired bullet is greater.
B) the dropped bullet is greater.
C) each bullet is 10 meters per second per second.

Answer: C

A car accelerates at 2 meters per second per second. Assuming the car starts from rest, how much time does it need to accelerate to a speed of 30 m/s?

A) 2 seconds
B) 15 seconds
C) 30 seconds
D) 60 seconds
E) none of these

Answer: B

Disregarding air resistance, objects fall with constant

A) velocity.
B) speed.
C) acceleration.
D) distances each successive second.

Answer: C

At one instant a heavy object in air is moving upward at 50 meters per second. One second later its speed is approximately

A) 40 m/s.
B) 50 m/s.
C) 55 m/s.
D) 60 m/s.

Answer: A

An object covers a distance of 8 meters in the first second of travel, another 8 meters during the next second, and 8 meters again during the third second. Its acceleration in meters per second per second is approximately

A) 0.
B) 5.
C) 8.
D) 24.

Answer: A

A ball tossed vertically upwards rises, reaches its highest point, and then falls back to its starting point. During this time the acceleration of the ball is always

A) opposite its velocity
B) directed upwards
C) directed downwards
D) in the direction of motion

Answer: C

If a rocket initially at rest accelerates at a rate of 50 m/s^2 for one minute, its speed will be

A) 3600 m/s
B) 50 m/s
C) 500 m/s
D) 3000 m/s

Answer: D

A heavy object and a light object are dropped at the same time from rest in a vacum. The heavier object reaches the ground

A) later than the lighter object
B) sooner than the lighter object
C) at the same time as the lighter object
D) almost immediately

Answer: C

The two measurements necessary for calculating average speed are

A) acceleration and time.
B) velocity and time.
C) distance and time.
D) distance and acceleration.
E) velocity and distance.

Answer: C

If an object moves with constant acceleration, its velocity must

A) be constant also.
B) change by the same amount each second.
C) change by varying amounts depending on its speed.
D) always decrease.

Answer: B

While an object near the Earth's surface is in free fall, its

A) velocity increases.
B) acceleration increases.
C) mass increases.
D) mass decreases.

Answer: A

A horse gallops a distance of 10 kilometers in a time of 30 minutes. It's average speed is

A) 20 km/h
B) 15 km/h
C) 30 km/h
D) 40 km/h

Answer: A

The last instant just before an airplane crashes a passenger jumps out the door and falls only two feet to the ground. The passenger

A) lucky to have studied physics
B) unharmed
C) probably hurt or killed
D) intelligent to think so fast

Answer: C

If no external forces are acting on a moving object, it will

A) continue moving at the same speed.
B) continue moving at the same velocity.
C) move slower and slower until it finally stops.

Answer: B

When a rocket ship accelerating in outer space runs out of fuel, it

A) accelerates for a short time, then slows down to a constant velocity.
B) accelerates for a short time, slows down, and eventually stops.
C) no longer accelerates.

Answer: C

A package falls off a truck that is moving at 30 m/s. Neglecting air resistance, the horizontal speed of the package just before it hits the ground is

A) zero.
B) less than 30 m/s but larger than zero.
C) about 30 m/s.
D) more than 30 m/s.
E) More information is needed for an estimate.

Answer: C

The gain in speed each second for a freely-falling object is about

A) 0
B) 10 m/s
C) 5 m/s
D) 20 m/s

Answer: B

A sheet of paper can be withdrawn from under a container of milk without toppling it if the paper is jerked quickly. This best demonstrates that

A) the milk carton has no acceleration.
B) there is an action-reaction pair of forces.
C) gravity tends to hold the milk carton secure.
D) the milk carton has inertia.
E) none of these

Answer: D