Physics Semester One Review

A ball is thrown upward at a speed at a speed of vi at an angle of 52 degrees above the horizontal. It reaches a maximum height of 7.5 m. How high would this ball go if it were thrown straight upward at speed vi?

12.1 m

An airplane starts from rest and reaches a takeoff velocity of 60 m/s due north in 4.0 seconds. How far has it traveled before takeoff?

120 m, due North

A 2 kg mass moving at 3 m/s hits a vertical wall and rebounds with the same speed. If the contact time with the wall is .01 seconds, the magnitude of the force exerted on the mass is most nearly.

1200 N

When a 58 g tennis ball is served, it accelerates from rest to a speed of 45 m/s. The impact with which the racket gives the ball a constant acceleration over a distance of 44 cm. What is the magnitude of the net force acting on the ball?

133 N

A .2 kg ball on a stick is whirled on a vertical circle at a constant speed. When the ball is at the three o'clock position, the stick tension is 16 N. Find the tensions in the stick when he ball is at the twelve and six o'clock positions.

14 N; 18 N

A satellite circles the earth in an orbit whose radius is twice the earth's radius. The earth's mass is 5.98x10^24 kg, and its radius is 6.38x10^6 m. What is the period of the satellite?

14300 seconds

What is the mass on Mercury of an object that weights 784 N on the Earth's surface?

80 kg

A particle moves along the +x axis, and the graph shows its momentum p as a function of time t. In each of the four regions a force, which may or may not be nearly zero is applied to the particle. In which region is the magnitude of the force largest and in which region is it the smallest?

C largest (biggest slope), B smallest (flat slope)

A ball is fixed to the end of a string, which is attached to the ceiling at point P. As the drawing shows, the ball is projected downward at A with the launch speed V0. Traveling on a circular path, the ball comes to a halt at point B. What enables the ball to reach point B, which is above point A? Ignore friction and air resistance.

The ball's kinetic energy

A satellite of mass m and speed v moves in a stable, circular orbit around a planet of mass M. What is the radius of the satellite's orbit?

(GM)/(v^2)

A railroad flatcar of mass 2000 kg rolls to the right at 10 m/s and collides with a flatcar of mass 3000 kg that is rolling to the left at 5 m/s. The flatcars couple together. Their speed after the collision is

1 m/s

A hot-air balloon is rising upward with a constant speed of 2.75 m/s. When the balloon is 3.00 m above the ground, the balloonist accidentally drops a compass over the side of the balloon. How much time elapses before the compass hits the ground?

1.11 seconds

A rock is dropped from the top of a 45 meter tower, and at the same time a ball is thrown from the top of the tower in a horizontal direction. Air resistance is negligible. The ball and the rock hit the level ground a distance of 30 meters apart. The horizontal velocity of the ball thrown was most nearly

10 m/s

In 1954 the English runner Roger Bannister broke the four minute barrier for the mile with a time of 3:59:.4. In 1999 the Moroccan runner Hicham el-Guerrouj set a record of 3:43:.13 s for the mile. If these two runners had run in the same race, each running the entire race at the average speed that earned him a place in the record books, el-Guerrouj would have won. By how many meters?

109-114 meters (around there)

A 95 kg person stands on a scale in an elevator. What is the apparent weight when the elevator is accelerating upward with an acceleration of 1.8 m/s^2?

1121 N

A skater with an initial speed of 7.6 m/s stops propelling himself and begins to coast across the ice, eventually coming to rest. Air resistance is negligible. The coefficient of kinetic friction between the ice and the skates is .1. How far will the skater travel before coming to rest?

29 meters

A criminal is escaping across a rooftop and runs off the roof horizontally at a speed of 5.3 m/s, hoping to land on the roof of the adjacent building. Air resistance is negligible. The horizontal distance between the two buildings is D, and the roof of the adjacent building is 2 meters below the jumping off point. Find the maximum value for D.

3.4 meters

A target T lies flat on the ground 3 meters from the side of a building that is 10 m tall, as show right. A student rolls a ball off the horizontal roof of the building in the direction of the target. Air resistance is negligible. The horizontal speed with which the ball must leave the roof if it is to strike the target is most nearly

3/square root of 2. or 2.14 m/s

The speed of the ball at point II is most nearly?

4.5 m/s

A cheetah is hunting. Its prey runs for 3.1s at a constant velocity of +8.1 m/s. Starting from rest what constant acceleration must the cheetah maintain in order to run the same distance as its prey runs in the same time?

5.2 m/s^2

Two objects , A and B, initially at rest, are "exploded" apart by the release of a coiled spring that was compressed between them. As they move apart, the velocity of object A is 5 m/s and the velocity of object B is 2 m/s. The ratio of the mass of object A to the mass of object B, mA/mB, is

5/2

A projectile is fired from the surface of the Earth with a speed of 200 meters per second at an angle of 30 degrees above the horizontal. If the ground is level, what is the maximum height reached by the projectile?

500 meters

A student weighing 700 N climbs at constant speed to the top of an 8 m vertical rope in 10 s. The average power expended by the student to overcome gravity is most nearly

560 W

The magnitude of the frictional force along the plane is most nearly

6 N

Which of the following diagrams best represents the gravitational force Fg, the frictional force Ff, and the normal force Fn that act on the block?

Fg point down, Fn perpendicular to the the object, Ff in the opposite direction of movement.

A block of weight Fg is pulled along a horizontal surface at constant speed v by a force Fa, which acts at an angle of theta with the horizontal, as shown above. The normal force exerted on the block by the surface has magnitude:

Fg-Fasin0

When an object of weight Fg is suspended from the center of a massless string as shown to the right, the tension at any point in the string is:

Fg/(2cos0)

A figure of a dancer on a music box moves counterclockwise at constant speed around the path shown above. The path is such that the lengths of its segments, PQ, QR, RS, and SP, are equal. Arcs QR and SP are semicircles. Which of the following best represents the magnitude of the dancer's acceleration as a function of time t during one trip around the path, beginning at point P ?

PQ is low, QR is flat and faster, RS is slower, SP is flat and faster.

A car initially travels north and then turns to the left along a circular curve. This causes a package on the seat of the car to slide toward the right side of the car. Which of the following is true of the net force on the package while it is sliding?

There is not enough force directed toward the center of the circle to keep the package from sliding

The velocity of a projectile at launch has a horizontal component Vv. Air resistance is negligible. When the projectile is at the highest point of its trajectory, which of the following show the vertical and horizontal components of its velocity and the vertical component of its acceleration?

Vertical velocity= 0 Horizontal velocity=Vh Vertical acceleration= g

Force F1 acts on a particle and does W1. Force F2 acts simultaneously on the particle and does work W2. The speed of the particle does not change. Which of the following must be true?

W1=-W2

In a race two horses start from rest and each maintains a constant acceleration. In the same elapsed time Silver Bullet runs 1.2 times farther than Shotgun. According to the equations of kinematics, which one of the following is true concerning the accelerations of the horses?

acceleration silver bullet= 1.2 acceleration shotgun

Each drawing to the right shows three points along the path of a projectile, one on its way up, on at the top, and one on its way down. The launch point is on the left in each drawing. Which drawing correctly represents the acceleration vector of the projectile at these three points?

all three arrows pointing down bc acceleration

If the potential energy is zero at point II, where will the kinetic and potential energies of the ball be equal?

at point III

a racing car is moving around the circular track of radius 300 m shown above. at the instant when the car's velocity is directed due east, its acceleration is directed due south and has a magnitude of 3 m/s2. when viewed from above, the car is moving

clockwise at 30 m/s

An object is thrown with velocity v on level ground. Neglect air resistance. In order for the object to travel a maximum horizontal distance before hitting the ground, the throw should be at an angle theta with respect to the horizontal of

exactly 45 degrees above the horizontal

An object slides off a roof 10 meters above the ground with an initial horizontal speed of 5 meters per second as shown above. The time between the object's leaving the roof and hitting the ground is most nearly

square root of 2 seconds

A projectile is launched from level ground with an initial speed v0 at an angle theta with the horizontal. If air resistance is negligible, how long will the projectile remain in the air?

t=2Visin0/g (0=theta)

A ball attached to a string is whirled around in a horizontal circle having a radius r. If the radius of the circle is changed to 4r and the same centripetal force is applied by the string, the new speed of the ball is which of the following?

twice the original speed

a push broom of mass m is pushed across a rough horizontal floor by a force of magnitude F directed at angle theta as shown to the right. The coefficient of friction between the broom and the floor is u. The frictional force on the broom has magnitude

u(mg+Fsin0)

In which one of the following situations can the equations of kinematics not be used?

when the acceleration changes from moment to moment

The horizontal turntable shown to the right rotates at a constant rate. As viewed from above, a coin on the turntable moves counterclockwise in a circle as shown. Which of the following vectors best represents the direction of the frictional force exerted on the coin by the turnable when the coin is in the position shown?

(opposite to the direction of the coin's movement) looks like the arrow is pointing down

A slower moving car is traveling behind a faster moving bus. The velocity of the car relative to ground is +12 m/s. The velocity of the bus relative to the ground is +16 m/s. A passenger on the bus gets up and walks towards the front of the bus with a velocity of +2 m/s relative to the bus. What is the velocity of the passenger relative to the car?

+6 m/s

Two rockets are flying in the same direction and are side by side at the instant their retrorockets fire. Rocket A has an initial velocity of +5200 m/s, while Rocket B has an initial velocity of +8760 m/s. After a time t both rockets are again side by side, the displacement of each being zero. The acceleration of rocket A is -16 m/^2. What is the acceleration of rocket B?

-26.95 m/s^2

A jetliner, traveling northward; is landing with a speed of 72 m/s. Once the jet touches down, it has 740 m of runway in which to reduce its speed to 6.1 m/s. Compute the average acceleration (magnitude and direction) of the plane during landing (take the positive direction to be northward).

-3.38 m/s^2

A boy jumps from rest, straight down from the top of a cliff. He falls halfway down to the water below in .679 seconds. How much time passes during his entire trip from the top down to the water? Ignore air resistance.

.56 seconds

At the beginning of a basketball game, a referee tossed the ball straight up with a speed of 6.7 m/s. A player cannot touch the ball until after it reaches its maximum height and begins to fall down. What is the minimum time that a player must wait before touching the ball?

.68 seconds

Speedboat A negotiates a curve whose radius is 120 m. Speedboat B negotiates a curve whose radius is 240 m. Each boat experiences the same centripetal acceleration. What is the ratio of Va/Vb of the speeds of the boats?

.71

Two forces act on a moving object that has a mass of 27 kg. One force has a magnitude of 12 N and points due South, while the other force has a magnitude of 17 N and points due West. What is the acceleration of the object?

.77 m/s^2, 35 degrees south of west

Two ice skaters, Paul and Tom, are each holding on to opposite ends of the same rope, Each pulls the other toward him. The magnitude of Paul's acceleration is 1.25 times greater than the magnitude of Tom's acceleration. What is the ratio of Paul's mass to Tom's mass?

.80

A woman is riding a jet ski at a speed of 26 m/s and notices a seawall straight ahead. The farthest she can lean the craft in order to make a turn is 22 degrees. This situation is like that of a car on a curve that is banked at an angle of 22 degrees. If she tries to make the turn without slowing down, what is the minimum distance from the seawall that she can begin making her turn and still avoid a crash?

170 m

A horizontal force F is used to pull a 5 kg block across a floor at a constant speed of 3 m/s. The frictional force between the block and the floor is 10 N. The work done by the force F in 1 minute is most nearly

1800 J

There is a clever kitchen gadget for drying lettuce leaves after you wash them. It consists of a cylindrical container mounted so that it can be rotated about its axis by turning a hand crank. The radius of the container is 12 cm. When the cylinder is rotating at 2 revolutions per second, what is the magnitude of the centripetal acceleration at the outer wall?

19 m/s^2

During which time interval is the particle described by these position graphs, to the right, at rest? (Hint: these graphs record position in x and y axes, so consider both)

2-3 s

The highest barrier a projectile can clear is 13.5 meters (thus the max height in y), when the projectile is launched at an angle of 15 degrees above the horizontal. What is closest to the projectile's launch speed? (the launcher and barrier base are at the same height)

63 m/s

The speed of a bobsled is increasing because it has an acceleration of 2.4 m/s^2. At a given instant in time, the forces resisting the motion, including kinetic friction and air resistance, total 450 N. The combined mass of the bobsled and its riders is 270 kg. What is the magnitude of the net force that acts on the bobsled?

648 N

A speed skater goes around a turn that has a radius of 31 m. The skater has a speed of 14 m/s and experiences a centripetal force of 460 N. What is the mass of the skater?

73 kg

The drawings to the right show three examples of the force with which someone pushes against a vertical wall. In each case the magnitude of the pushing force is the same. Rank the normal forces that the wall applies to the pusher in ascending order (smallest first).

B (smallest angle w the vertical), A (medium angle), C (biggest angle)

Two balls are thrown from the top of a building. Ball 1 is thrown straight down and ball 2 is thrown with the same speed but upward at an angle theta with respect to the horizontal (see picture to the right). Consider the motion of the balls after they are released. Which one of the following statements is true?

Both balls have the same acceleration at all times

Two cars are traveling at the same constant speed v. Car A is moving along a straight section of the road while car B is rounding a circular turn. Which statement about their accelerations is true?

Car A is not accelerating, but Car B is accelerating

Which one of the following statements is not true? A) in free-fall motion near the earth's surface the acceleration is the acceleration due to gravity B) in the absence of air resistance the motion of a baseball after being thrown straight upward from the ground is an example of free-fall C) The equations of kinematics apply to free-fall motion D) in the absence of air resistance the motion of the baseball dropped from rest from the top of a building is an example of free-fall E) Near the earth's surface the acceleration due to gravity has the approximate magnitude of 9.8 m/s^2, points downward when the motion is downward, and points upward when the motion is upward.

E

When the frictionless system show to the right is accelerated by an applied force of magnitude F, the tension in the string between the blocks is

F/3

The drawing to the right shows an extreme skier at the bottom of a ski jump. At this point the track is circular with a radius r. Two forces act on the skier, her weight and the normal force. Which relation describes how the net force acting on her is related to her mass m and speed v to the radius r?

Fn-mg=mv^2

How does an air mattress protect a stunt person landing on the ground after a stunt?

It lengthens the stopping time of the stunt person and reduces the force applied during the landing

From the top of a high cliff, a ball is thrown horizontally with initial speed v0. Which of the following graphs best represents the ball's kinetic energy K as a function of time t?

Starting further up on the graph, exponential slope, not linear

A ball of mass m is suspended from two strings of unequal length as shown to the right. The tensions T1 and T2 in the strings must satisfy which of the following relations?

T1<T2

Two identical stones attached to cords that are being whirled on a tabletop at the same speed. The radius of the larger circle is twice that of the smaller circle. How is the T1 in the longer cord related to the tension T2 in the shorter cord?

T1=(1/2)T2

Two people are in a boat that is capable of a maximum speed of 5 kilometers per hour in still water, and wish to cross a river 1 kilometer wide to a point directly across from their starting point. If the speed of the water in the river is 5 kilometers per hour, how much time is required for the crossing?

The point directly across from the starting point cannot be reached under these conditions.

Which of the following is true when an object of mass m moving on a horizontal frictionless surface hits and sticks to an object of mass M>m, which is initially at rest on the surface?

The speed of the objects that are stuck together will be less than the initial speed of the less-massive object

The top of a cliff is located a distance H above the ground. At a distance H/2 there is a branch that juts out from the side of a cliff, and on this branch a bird's nest is located. A stone is thrown at the nest with the same initial speed, either straight downward from the top of the cliff or straight upward from the ground. In the absence of air resistance, which stone hits the nest in the least amount of time?

The stone thrown from the top of the cliff