Physics Multiple Choice 2

The "retain" foce does not cancel out the "action" force because:

they act on different bodies

An object is moving on a circular path of radius π meters at a constant speed of 4.0m/s. The time required for one revolution is:

π²/2s

A box rests on a rough board 10m long. When one end of the board is slowly raised to a height of 6m above the other end, the box begins to slide. The coefficient of static friction is:

.75

A forwards force of 12N is used to pull a 240N sled at constant velocity on a frozen pond. The coefficient of friction is:

0.05

A car is traveling at 15m/s on a horizontal road. The brakes are applied and the car skids to a stop in 4s. The coefficient of kinetic friction between the tires and the road is:

0.38

The unit of force called the newton is:

1 kgm/s²

Two forces are applied to a 5 kg object; one is 6 N to the north and other is 8 N to the west. The magnitude of the acceleration of the object is:

2m/s²

A giant wheel, having a diameter of 40m, is fitted with a cage and platform on which a man of mass m stands. The wheel rotates in a vertical plane at such a speed that the force exerted by the man on the platform is equal to his weight when the cage is at X, as shown. The net force on the man at point X is:

2mg down

A crane operator lowers a 16,000 N steel ball with a downward accelerate of 3m/s². The tension in the cable isL

11,000N

A 1000 kg elevator is rising and its speed is increasing at 3m/s². The tension in the elevator cable is:

12800N

For a biological sample in a 1.0m radius centrifuge to have a centripetal acceleration of 25g its speed is m/s must be:

16

A 6 kg object is moving south. A net force of 12N north is acting on it will result in the object having an acceleration of:

2 m/s² north

Block A, with a mass of 50kg rests on a horizontal table top. The coefficient of static friction is 0.40. A horizontal string attached to A passes over a massless, frictionless pulley as shown. The smallest mass that will start A moving when it is attached to the other end of the string is:

20 kg

A car rounds a 75m radius curve at a constant speed of 18 m/s. A ball is suspended by a string from the ceiling of the car and moves with the car. The angle between the string and the vertical is:

24⁰

a box with a weight of 50N rests on a horizontal surface. A person pulls horizontally on it with a force of 10 N and it does not move. To start it moving, a second person pulls vertically upwards on the box. If the coefficient of static friction is 0.4, what is the smallest vertical force for which the box moves?

25

An 800N passenger in a car, presses against the car door with a 200N force when the car makes a left hand turn at 13 m/s. The door will pop open under a force of 800N. Of the following, the least speed for which the man is thrown out of the car is:

26 m/s

An object moves in a circle. If the mass is tripled, the speed halved and the radius unchanged then the centripetal force must be:

3/4

A 0.2kg stone is attached to a string and swung in a circle of radius 0.6m on a horizontal and frictionless surface. If the stone makes 150 revolutions per minute, the tension force of the string is:

30N Ft=mV²/r

A stone is tied to a 0.5m string and whirled at constant speed of4.0 m/s in a vertical circle. Its acceleration in m/s² at the top of the circle is:

32 down

In a tug-of-war, two men each pull on the rope with 400N forces, in opposite directions. The tension in the rope is:

400N

A 700kg elevator accelerates downward 3m/s². The tension force of the cable on the elevator is:

4900N up Ft-Fg=ma Ft=mg+ma

If a certain car, going with speed v, rounds a level curve with a radius R, it is just on the verge of skidding. If its speed is now doubled, the radius of the tightest curve on the same road that it can round without skidding is:

4R

When a certain force is applied to the 1kg standard mass its acceleration is 5.0 m/s². When the same force is applied to another object its acceleration is 1/5 as much. The mass of the object is:

5.0 kg

The standard 1kg mass is attached to a compressed spring and the spring is released. If the mass initially has an acceleration of 5.6m/s², the force of the spring has a magnitude of:

5.6N F=ma

A car starts from Hither, goes 50kg in a straight line to Yon, immediately turns around and returns to Hither. The time for this round trip is 2hrs. The average speed of the car for this round trip is:

50km/h

One end of a 1m long string is fixed, the other end is attached to a 2kg stone. The stone swings in a vertical circle, passing the bottom point at 4 m/s. The tension force of the string at this point is about:

52 -2N + Ft = (2kg)(16m/s)

A 90kg man stands in an elevator that is moving up at a constant speed of 5m/s. The force exerted by him on the floor is about:

880N

An 1.5 N ball is thrown at an angle of 30⁰ above the horizontal with an initial speed of 12m/s. At its highest point, the net force on the ball is:

9.8N down

Which of the following quantities is NOT a vector? a. mass b. displacement c. weight d. acceleration e. force

a. mass

A physics textbook is suspended on a spring scale in an elevator. Of the following, the scale shows the highest reading when the elevator: a. moves upward with increasing speed b. moves upward with decreasing speed c. remains stationary d. moves downward with increasing speed e. moves downward at constant speed

a. moves upward with increasing speed

A brick slides on a horizontal surface. Which of the following will increase the frictional force on it? a. putting a second brick on top b. decreasing the surface area of contact c. increasing the surface area of contact d. decreasing the mass of the brick e. none of the above

a. putting a second brick on top

A block is first placed on its long side and then on its short side on the same inclined plane. The block slides down the plant on its short side but remains at rest on its long side. A possible explanation is: a. the short side is smoother b. Force friction is less because contact area is lead c. the center of gravity is higher in the second case d. the normal force is less in the second case e. the force of gravity is more nearly down the plane in the second place

a. the short side is smoother

An object rests on a horizontal frictionless surface. A horizontal force of magnitude F is applied. This force produces an acceleration:

always

A person riding a Ferris wheel is strapped into her seat by a seat belt. The wheel is spun so that the centripetal acceleration is g. Selected the correct combination of forces that act on her when she is at the top. Fg=force of gravity, down; Fb=seat belt force, down; Fs=seat force, up. a. Fg=0, Fb=mg, Fs=0 b. Fg=mg, Fb=0, Fs=0 c. Fg=0, Fb=0, Fs=mg d. Fg=mg, Fb=mg, Fs=0 e. Fg=mg, Fb=0, Fs= mg

b. Fg=mg, Fb=0, Fs=0

A physics textbook is suspended on a spring scale in an elevator. Of the following, the scale shows the highest reading when the elevator: a. moves downward with increasing speed b. moves downward with decreasing speed c. remains stationary d. moves upward with decreasing speed e. moves upward at constant speed

b. moves downward with decreasing speed

Mass differs from weight in that: a. all objects have weight but some lack mass b. weight is a force and mass is not c. the mass of an object is always more than its weight d. mass can only be expressed in the metric system e. there is no difference

b. weight is a force and mass is not

A lead block is suspended from your hand by a string. The reaction to the force of gravity on the block is the force exerted by the:

block on the Earth

Two objects are traveling around different circular orbits with constant speed. They both have the same acceleration but object A is traveling twice as fast as object B. The orbit radius for object A is ______ the orbit radius for object B.

four times

A force F, larger than the largest possible force of static friction, is applied to the left to an object moving to the right on a horizontal surface. Then: a. the object must be moving at constant speed b. F and the friction force act in opposite directions c. the object must be slowing down d. the object must be speeding up e. the object must come to rest and remain at rest

c. the object must be slowing down

An object moving in a circle at constant speed: a. must only have one force acting on it b. is not accelerating c. is held to its path by centrifugal force d. has an acceleration of constant magnitude e. has an acceleration tangent to the circle

d. has an acceleration of constant magnitude

A professor holds an eraser against a vertical chalkboard by pushing horizontally on it. He pushes with a force that is much greater than is required to hold the eraser. The force friction exerted by the board on the eraser increases if he: a. pushed with a slightly greater force b. pushed with a slightly less force c. stops pushing d. raises his elbow so the force he exerts is slightly downward but has the same magnitude e. lowers his elbow so the force he exerts is slightly upward but has the same magnitude

d. raises his elbow so the force he exerts is slightly downward but has the same magnitude

Which of the following is not an example of accelerated motion? a. vertical component of projectile motion b. circular motion at constant speed c. a swinging pendulum d. Earth's motion about the sun e. horizontal component of projectile motion

e. horizontal component of projectile motion

If a satellite moves above the Earth's atmosphere in a circular orbit with constant speed, then: a. its acceleration and velocity are in the same direction b. the net force on it is zero c. its velocity is constant d. it will fall back to Earth when its fuel is used up e. its acceleration is toward the Earth

e. its acceleration is toward the Earth

Which of the following is a vector quantity? a. mass b. density c. speed d. temperature e. none of these

e. none

An object of mass m and other object of mass @m are each forced to move along a circle of radius 1.0m at a constant speed of 1.0m/s². The magnitudes of their acceleration are:

equal a = V²/r

A coin is placed on a horizontal phonograph turntable. Let N be the normal force exerted by turntable on the coin, f be the frictional force exerted by the turntable on the coin, and fs be the maximum force of static friction. The speed of the turntable is increased in small steps. It the coin does not slide then

f increases and both N and Fs stay the same

A stone is tied to a string and whirled at constant speed in a horizontal circle. The speed is then doubled without changing the length of the string. Afterward, the magnitude of the acceleration of the stone is:

four times as great

An object moves in a circle. If the radius doubled keeping the speed the same then the centripetal force must be:

half as great

An object moves in a circle. If the radius is doubled keeping the speed the same then the centripetal force must be:

half as great

The term "mass" refers to the same physical concept as:

inertia

The mass of a body:

is independent of the acceleration due to gravity

Two objects, one having three times the mass of the other, are dropped from the same height in a vacuum. At the end of their fall, their velocities are equal because: a. anything falling in a vacuum has constant velocity b. all objects reach the same terminal velocity c. the acceleration of the larger object is three times greater than that of the smaller object d. the force of gravity is the same for both objects

none of the above

A particle moves at constant speed in a circular path. The instantaneous velocity and instantaneous acceleration vectors are:

perpendicular to each other

The driver of a 1000kg car tries to turn through a circle of radius 100m on an unbanked curve at a speed of 100m/s. The actual frictional force between the tires and slippery road is 900N. The car will:

slide off to the outside of the curve

A newton is the force:

that gives 1kg body an acceleration of 1m/s²

A book rests on a table, exerting a downward force on the table. The reaction to this force is:

the force of the table on the book

A feather and a lead ball are dropped from rest in a vacuum on the moon. The acceleration of the feather is:

the same as of the of the lead ball

Equal forces F act on isolated bodes A and B. The mass of B is three times that of A. The magnitude of the acceleration of A is:

three times that of b

A 1000kg airplane moves in straight flight at constant speed. The force of air friction is 1800N. The net force on the plane is:

zero

A heavy steel ball B is suspended by a cord from a block of wood W. The entire system is dropped through the air. Neglecting air resistance, the tension in the cord is:

zero