2nd Period Review

A player kicks a soccer ball in a high arc toward the opponent's goal. At the highest point in its trajectory

neither the ball's velocity nor its acceleration are zero.

A projectile is launched with an initial velocity of 80 m/s at 30° above the horizontal. Neglecting air, what is horizontal component of the projectile's acceleration?

0 m/s^2

As a 70-kg person stands at the seashore gazing at the tides (which are caused by the Moon), how large is the gravitational force on that person due to the Moon? The mass of the Moon is 7.35 × 1022 kg, the distance to the Moon is 3.82 × 108 m, and G = 6.67 × 10-11 N ∙ m2/kg2.

0.0024 N

Two air track carts move along an air track towards each other. Cart A has a mass of 450 g and moves toward the right with a speed of 0.850 m/s. Cart B has a mass of 300 g and moves toward the left with a speed of 1.12 m/s. What is the total momentum of the two-cart system?

0.047 kg ∙ m/s toward the right

A 50.0-kg crate is being pulled along a horizontal smooth surface. The pulling force is 10.0 N and is directed 20.0° above the horizontal. What is the magnitude of the acceleration of the crate?

0.188 m/s^2

An object slides on a level floor. It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s2. What is the coefficient of kinetic friction between the object and the floor?

0.24

Two ice skaters suddenly push off against one another starting from a stationary position. The 45-kg skater acquires a speed of 0.375 m/s relative to the ice. What speed does the 60-kg skater acquire relative to the ice?

0.28 m/s

A cat leaps to try to catch a bird. If the cat's jump was at 60° off the ground and its initial velocity was 2.74 m/s, what is the highest point of its trajectory, neglecting effects of air?

0.29 m

A 0.140-kg baseball is dropped and reaches a speed of 1.20 m/s just before it hits the ground and bounces. It rebounds with an upward velocity of 1.00 m/s. What is the change of the ball's momentum during the bounce?

0.308 kg

A 0.14-kg baseball is dropped from rest from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance?

0.88 kg ∙ m/s

At their closest approach, Venus and Earth are 4.20 × 10^10 m apart. The mass of Venus is 4.87 × 10^24 kg, the mass of Earth is 5.97 × 10^24 kg, and G = 6.67 × 10^-11 N ∙ m^2/kg^2. What is the magnitude of the gravitational force exerted by Venus on Earth at that point?

1.10 x 10^18 N

In another solar system, a planet has an airless moon Zygo that is 4.0 × 10^5 m in diameter. Experiments reveal that a freely falling object at the surface of Zygo accelerates at 0.20 m/s^2. What is the mass of Zygo? (G = 6.67 × 10^-11 N ∙ m^2/kg^2)

1.2 x 10^20kg

Suppose NASA wants a satellite to revolve around Earth 5 times a day. What should be the radius of its orbit if we neglect the presence of the Moon? (G = 6.67 × 10^-11 N ∙ m^2/kg^2, M earth = 5.97 × 10^24 kg)

1.44 x 10^7 m

Suppose our sun had 4 times its present mass but the earth orbited it at the same distance as it presently does. What would be the length of the year on the earth under those conditions?

1/2 as long as the present year

A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal. If we can neglect air, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

10 m/s

A net force accelerates a 4.5-kg tool at 40 m/s^2. What acceleration would that same net force cause if it were exerted on an 18-kg tool?

10 m/s^2

A block is on a frictionless table, on Earth. The block accelerates at 3.0 m/s^2 when a 20 N horizontal force is exerted on it. The block and table are set up on the Moon where the freefall acceleration is 1.62 m/s2. The gravitational force exerted on the block by the Moon is closest to

11 N

The x component of vector is 8.7 units, and its y component is -6.5 units. The magnitude of is closest to

11 units

A particularly scary roller coaster contains a loop-the-loop in which the car and rider are completely upside down. If the radius of the loop is 13.2 m, what minimum speed must the car have at the top of the loop so that the rider does not fall out while upside down at the top? Assume the rider is not strapped to the car.

11.4 m/s

A 328-kg car moving at 19.1 m/s in the +x direction hits from behind a second car moving at 13.0 m/s in the same direction. If the second car has a mass of 790 kg and a speed of 15.1 m/s right after the collision, what is the velocity of the first car after this sudden collision?

14.0 m/s

A displacement vector is 34.0 m in length and is directed 60.0° east of north. Selecting from the choices in the table below, what are the components of this vector? Northward Eastward

17.0 m 29.4 m

The conical pendulum shown above swings in a circle of radius 0.60 m and speed 1.4 m/s. What angle does the string make with the vertical?

18

A boy jumps with a velocity of magnitude 20.0 m/s at an angle of 25.0° above the horizontal. What is the horizontal component of the boy's velocity?

18.1 m/s

A firecracker breaks up into two pieces, one of which has a mass of 200 g and flies off along the +x-axis with a speed of 82.0 m/s. The second piece has a mass of 300 g and flies off along the +y-axis with a speed of 45.0 m/s. What is the total momentum of the two pieces?

21.2 kg ∙ m/s at 39.5° from the +x-axis

An object moves 15.0 m north and then 11.0 m south. Find both the path length it has traveled and the magnitude of its displacement.

26.0 m, 4.0 m

You throw a rock horizontally off a cliff with a speed of 20 m/s. Assuming no effects of air, after 2.0 s, the magnitude of the velocity of the rock is closest to

28 m/s

One way that future space stations may create artificial gravity is by rotating the station. Consider a cylindrical space station 380 m in diameter that is rotating about its longitudinal axis. Astronauts walk on the inside surface of the space station. How long will it take for each rotation of the cylinder if it is to provide "normal" gravity for the astronauts?

28 s

A 600-kg car is going around a banked curve with a radius of 110 m at a steady speed of 24.5 m/s. What is the appropriate banking angle so that the car stays on its path without the assistance of friction?

29.1°

A 6.0-kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If the coefficient of kinetic friction is 0.40, at what rate does the box accelerate down the slope?

3.1 m/s^2

Two small objects, with masses m and M, are originally a distance r apart, and the gravitational force on each one has magnitude F. The second object has its mass changed to 2M, and the distance is changed to r/4. What is the magnitude of the new gravitational force?

32F

The x component of vector is 5.3 units, and its y component is -2.3 units. The angle that vector makes with the +x-axis is closest to

340°

A car moving at a steady 10 m/s on a level highway encounters a bump that has a circular profile with a radius of 30 m. The car maintains its speed over the bump. What is the normal force exerted by the seat of the car on a 60.0-kg passenger when the car is at the top of the bump?

390 N

A 450-kg sports car accelerates from rest to 100 km/h in 4.80 s. What is the magnitude of the net force exerted on a 68.0-kg passenger during the acceleration?

394 N

A tiger is running in a straight line. If we double both the mass and speed of the tiger, by what factor will the magnitude of its momentum increase?

4

Mithra is an unknown planet that has two moons, A and B, in circular orbits around it, lying in the same plane. The table summarizes the hypothetical data about these moons. What is the magnitude of the maximum gravitational force that Moon A exerts on Moon B? (G = 6.67 × 10-11 N ∙ m2/kg2)

4.0 x 10^14

Two planets have the same freefall acceleration at the surface, but planet B has twice the radius of planet A. If planet A has mass m, what is the mass of planet B?

4m

A person is using a rope to lower a 0.51-kg bucket into a well with a constant speed of 2.0 m/s. What is the magnitude of the force exerted by the rope on the bucket?

5.0 N

A dinner plate falls vertically to the floor and breaks up into three pieces, which slide horizontally along the floor. Immediately after the impact, a 200-g piece moves along the +x-axis with a speed of 2.00 m/s, a 235-g piece moves along the +y-axis with a speed of 1.50 m/s. The third piece has a mass of 100 g. What is the speed of the third piece?

5.33 m/s

Astronaut Jennifer's lifeline to her spaceship comes loose and she finds herself stranded, "floating" 100 m from the mothership. She suddenly throws her 2.00-kg wrench at 20 m/s in a direction away from the ship. If she and her spacesuit have a combined mass of 200 kg, how long does it take her to coast back to her spaceship?

500 s

The curved section of a horizontal highway is a circular unbanked arc of radius 740 m. If the coefficient of static friction between this roadway and typical tires is 0.40, what would be the maximum safe driving speed for this horizontal curved section of highway?

54 m/s

An object moves with a constant speed of 30 m/s on a circular track of radius 150 m. What is the acceleration of the object?

6.0 m/s^2

An object moves with a constant speed of 30 m/s on a circular track of radius 150 m. What is the magnitude of the acceleration of the object?

6.0 m/s^2

A 1200-kg ore cart is rolling at 10.8 m/s across a flat friction-free surface. A crane suddenly drops 858 kg of ore vertically into the cart. How fast does the cart move just after being loaded with the ore?

6.30 m/s

What must be your average speed in order to travel 350 km in 5.15 h?

68.0 km/h

A hobbyist launches a projectile from ground level on a horizontal plain. It reaches a maximum height of 72.3 m and lands 111 m from the launch point. Assume no air. What was the angle of launch if g = 9.80 m/s2?

69.0°

A car of mass 1100 kg that is traveling at 27 m/s starts to slow down and comes to a complete stop in 578 m. What is the magnitude of the average stopping force exerted on the car?

690 N

In a popular carnival ride called The Centrifuge, shown above, riders stand against the inside wall of a large cylinder, which starts spinning. The radius of the circle traveled by the riders is 5.0 m. The coefficient of static friction between a person's shirt and the wall of the ride is 0.8. At what speed must the riders be moving to not slip downward when the floor lowers?

7.8 m/s

When rolled down a mountainside at 7.0 m/s, the horizontal component of its velocity vector was 1.8 m/s. What was the angle of the mountain surface above the horizontal?

75°

The components of vectors and are given as follows: Bx = -9.2 Cx = -4.5 By = -6.1 Cy = 4.3 The angle (less than 180°) between vectors and is closest to

77°

A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible air effects?

8.1 m/s

As shown in the figure, a 10-kg block on a perfectly smooth horizontal table is connected by a horizontal string to a 63-kg block that is hanging over the edge of the table. What is the magnitude of the acceleration of the 10-kg block when the other block is gently released?

8.5 m/s^2

If you are driving 72 km/h along a straight road and you look to the side for 4.0 s, how far do you travel during this inattentive period?

80m

You push downward on a trunk at an angle 25° below the horizontal with a force of 750 N. If the trunk is on a flat surface and the coefficient of static friction between the surface and the trunk is 0.61, what is the most massive trunk you will be able to move?

81 kg

A jet plane flying 600 m/s experiences an acceleration of 4.0 g when pulling out of the circular section of a dive. What is the radius of curvature of this section of the dive?

9.2 km

A boy kicks a football with an initial velocity of 20 m/s at an angle of 25° above the horizontal. If we neglect air, the magnitude of the acceleration of the ball while it is in flight is

9.8 m/s^2

A 1000-kg car is moving at 30 m/s around a horizontal unbanked curve with a diameter of 0.20 km. What is the magnitude of the friction force required to keep the car from sliding?

9000 N

If a vector A has components Ax < 0, and Ay > 0, then the angle that this vector makes with the positive x-axis must be in the range

90° to 180°

A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s. What is the height of the cliff if effects of air are negligible?

91 m

Two cars of equal mass have a head-on collision during a safety test. Car A has an initial velocity of 40 m/s, and car B has an initial velocity of -20 m/s. Which of the following choices describes the forces exerted by the cars on one another during the collision?

A exerts equal magnitude force on B as B exerts on A.

Two identical cars are moving with equal speeds on a wet road toward a turn, as shown in the figure above. Car A is on the left, and Car B is on the right. Which car is more likely to slide off the road during the turn and why, assuming their speeds remain unchanged?

Car A, because it moves through the turn with a smaller radius.

If a vector pointing upward has a positive magnitude, a vector pointing downward has a negative magnitude.

False

Mary and Debra stand on a snow-covered roof. They both throw snowballs with the same initial speed, but in different directions. Mary throws her snowball downward, at 30° below the horizontal; Debra throws her snowball upward, at 30° above the horizontal. Which of the following statements are true about just before the snowballs reach the ground below? Neglect the effects of air. (There could be more than one correct choice.)

Debra's snowball has exactly the same acceleration as Mary's snowball. Debra's snowball will stay in flight longer than Mary's snowball.

Two small spheres, A and B, attract each other gravitationally with a force of magnitude F. If we now double both masses and the separation of the spheres, what will now be the magnitude of the attractive force on each one?

F

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about the force of static friction f exerted on the block?

F = mg sin θ

If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out. This happens because an outward force balances the gravitational force exerted on the water.

False

In order to get a stationary object to start moving on a frictionless horizontal surface, you must exert a greater magnitude horizontal force on the object than the horizontal force that it exerts on you.

False

The Moon is accelerating toward Earth, so it is gradually getting closer to Earth.

False: It is not gradually approaching.

A spaceship is traveling to the Moon. At what point is it beyond the pull of Earth's gravity?

It is never beyond the pull of Earth's gravity

During a head-on collision, how does an air bag protect a passenger in the car?

It lengthens the stopping time interval for the passenger, and decreases the force exerted on them during the collision.

A 5-kg cart is being pushed by a constant horizontal force on a frictionless surface. What would happen to the cart if the pushing force exerted on it were doubled in magnitude?

Its acceleration would double

A car travels at constant speed along a banked, circular racetrack, shown above. The car is coasting around a turn, with negligible friction. Which of the following statements correctly relates the magnitude of the gravitational and normal forces exerted on the car?

N > mg

As shown in the figure, a woman is straining to lift a large crate, but without success. We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person, C is the magnitude of the vertical contact force on the crate by the floor, and W is the force that Earth exerts on the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

P + C = W

As a person is sliding down a vertical rope, her grip steadily tightens. This action causes the upward frictional force that the rope exerts on her to increase also. What happens when the upward frictional force is exactly equal in magnitude the force exerted on her by Earth?

She will move at constant velocity

Two boxes are connected to each other by a string as shown in the figure. The 10-N box slides without friction on the horizontal table surface. The pulley is ideal and the string has negligible mass. What is true about the tension force T that the string exerts on the boxes?

T < 30 N

Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled.

The displacement is either less than or equal to the path length traveled.

A hammer strikes a nail, driving it farther into a block of wood. Which of the following is the Newton's Third Law pair to the force that the hammer exerts on the nail?

The force that the nail exerts on the hammer

Consider two less-than-desirable options. In the first you are driving 30 mi/h and crash head-on into an identical car also going 30 mi/h. In the second option you are driving 30 mi/h and crash head-on into a stationary brick wall which your car does not even dent. In neither case does your car bounce back from the thing it hits, and the collision time interval is the same in both cases. Which of these two situations would result in the greater force on your car?

The force would be the same in both cases

Which of the following statements are true about an object in two-dimensional projectile motion if we neglect air?

The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

A small car collides head-on with a large truck. The two vehicles become permanently entangled. Which of the following statements concerning the magnitude of the average force during the collision is correct?

The small car and the truck experience average forces of the same magnitude.

A small car collides head-on with a large truck and the two vehicles become permanently entangled. Which of the following statements concerning the magnitude of the momentum change during the collision is correct? (There could be more than one correct choice.)

The small car and the truck experience the same magnitude momentum change.

Two objects have masses m and 5m, respectively. They both are placed side by side on a frictionless inclined ramp and allowed to slide down from rest without any air resistance. Which one of the following statements about these objects is correct?

The two objects reach the bottom of the ramp at exactly the same time.

An object moves in a circular path at a constant speed. Compare the direction of the object's velocity and acceleration vectors.

The vectors are perpendicular to each other

Vector A is along the +x-axis and vector B is along the +y-axis. Which one of the following statements is correct with respect to these vectors?

The y component of vector A is equal to the x component of vector B.

In an air-free chamber, a pebble is thrown horizontally, and at the same instant a second pebble is dropped from the same height. Compare the times of fall of the two pebbles.

They hit at the same time.

A boulder rolls off of a very high cliff. If you disregard air, while it is falling, its trajectory is never truly vertical.

True

The magnitude of a vector can never be less than the magnitude of any of its components.

True

A person is pushing on a box exerting a force of magnitude P, as shown in the figure. Earth exerts a force W on the box. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The force that the surface exerts on the box perpendicular to the surface is equal to

W + P sin θ.

If the position versus time graph of an object is a vertical line, the object is

at rest

The area under a curve in a velocity versus time graph gives

displacement

A space station, depicted above, rotates so that people in the outer ring, at a radius 2r from the center, experience a radial acceleration of constant magnitude g. What will be the magnitude of the radial acceleration experienced by people in the inner ring, at radius r from the center?

g/2

A satellite encircles Mars at a distance above its surface equal to 3 times the radius of Mars. If gm is the acceleration due to gravity at the surface of Mars, what is the acceleration due to gravity at the location of the satellite?

gm/16

For general projectile motion if we neglect air, the horizontal component of a projectile's acceleration

is always zero

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is exerted on box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

less than F but no zero

You are making a circular turn in your car on a horizontal road when you hit a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it

moves along a straight-line path in its original direction

You are making a circular turn in your car on a horizontal road when you come to a big patch of ice, causing the force of friction between the tires and the road to become zero. While the car is on the ice, it

moves along a straight-line path in its original direction.

If a velocity-time graph of an object is a horizontal line, the object is

moving with constant velocity

Identical net forces are exerted for the same time interval on two different objects. The magnitude of the change in momentum of the less-massive object is

precisely equal to the magnitude of the change in momentum of the more-massive object.

Two friends are standing on opposite ends of a canoe that is initially at rest with respect to a frictionless lake. The person in the front throws a very massive ball toward the back, and the person in the back catches it. After the ball is caught, the canoe is

stationary

The reason an astronaut in an earth satellite feels weightless is that

the astronaut is falling

The slope of a position time graph gives

velocity

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall. The ball bounces back with nearly the same speed with which it hits. The clay sticks to the wall. Which one of these objects undergoes the greater momentum change?

the ball

When a car goes around a banked circular curve on a horizontal road at constant speed, what force causes it to follow the circular path?

the friction force from the road

When a car goes around a circular curve on a horizontal road at constant speed, what force causes it to follow the circular path?

the friction force from the road

When a car goes around a banked circular curve at the proper speed speed for the banking angle, what force cause it to follow the circular path?

the normal force from the road

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Assuming no effects of air, when they reach the lake below

the splashdown speed of John is larger than that of James.

During World War I, Germany used a "Big Bertha" cannon to hurl shells into Paris 30 miles away. This gun had a very long barrel. What was the reason for using a long barrel in these guns?

to allow the force of the expanding gases from the gunpowder to act for a longer time interval