# physics kinematics

Suppose that a car traveling to the west (-x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?

A) its acceleration is positive

For general projectile motion with no air resistance, the vertical component of a projectile's acceleration

B) remains a non-zero constant

An airplane travels at 300 mi/hr south for 2.00 hours then at 250 mi/hr north for 750 miles. What is the average speed for the trip? a. 270 mi/hr b. 210 mi/hr c. 380 mi/hr d. 175 mi/hr

a. 270 mi/hr

SOH CAH TOA

opp/hyp adj/hyp opp/ajd

A water rocket can reach a speed of 75 m/s in 0.050 seconds from launch. What is its average acceleration?

A) 1500 m/s squared

Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance?

*The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward* The speed of the object is constant, but its velocity is not constant The speed of an object is zero at its highest point The acceleration of the object is +g when the object is rising and -g when it is falling

If 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

90-180

Which of the following quantities has units of a displacement? (There could be more than one correct choice.) a. 32 ft/s2 vertically downward b. 40 km southwest c. 9.8 m/s2 d. -120 m/s e. 186,000 mi

B and E

Which of the following quantities has units of a velocity? (There could be more than one correct choice.) a. 40 km southwest b. -120 m/s c. 9.8 m/s2 downward d. 186,000 mi e. 9.8 m/s downward

B and E

If, in the figure, you start from the Bakery, travel to the Café, and then to the Art Gallery (I) what distance you have traveled? (II) what is your displacement?

B) (I) 10.5 km (II) 2.50 km south

A child standing on a bridge throws a rock straight down. The rock leaves the child's hand at time t=0 s. If we take upward as the positive direction , which of the graphs shown below best represents the acceleration of the stone as a function of time?

B) *straight line in the negative part of the graph

A player hits a tennis ball into the air with an initial velocity of 32 m/s at 35 degrees from the horizontal. How fast is the ball moving at the highest point in its trajectory if air resistance is negligible?

B) 26 m/s

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

B) 26.0 m, 4.0 m

A motorist travels for 3.0 h at 80 km/h and 2.0 h at 100 km/h. What is her average speed for the trip?

B) 88 km/h

Under what condition is average velocity equal to the average of the object's initial and final velocity?

B) The acceleration is constant

A pilot drops a package from a plane flying horizontally at a constant speed. Neglecting air resistance, when the package hits the ground the horizontal location of the plane will

B) be directly over the package

An astronaut throws a discus on the moon where the acceleration due to gravity Is 1/6 what is it on earth. He throws the discus with an initial velocity of 20 m/s at an angle of 60 degrees from the horizontal. Neglecting air resistance and the height of the discus at the point of release, what is the range of the discus?

C) 212 m

A racquetball strikes a wall with a speed of 30 m/s and rebounds in the opposite direction with a speed of 26 m/s. The collision takes 20ms. What is the average acceleration of the ball during the collision with the wall?

C) 2800 m/s squared

A runner ran the marathon (approximately 42.0 km) in 2 hours and 57 min. What was the average speed of the runner in m/s?

C) 3.95 m/s

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 resistance?

C) 8.1 m/s

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

C) The displacement is either less than or equal to the distance traveled

Which of the following graphs represent an object having zero acceleration?

C) graph a and b

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experiences any air resistance?

C) the ball

James and John drive 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. If there is no air resistance, when they reach the lake below

C) the splashdown speed of John is larger than that of James

Check out #13

Check out #13

c

Consider two vectors shown in the figure. The difference A - B is best illustrated by

A rock from a volcanic eruption is launched straight up into the air with no appreciable air resistance. Which one of the following statements about this rock while it is in the air is correct? a. On the way up, its acceleration is downward and its velocity is upward, and at the highest point both its velocity and acceleration are zero. b. On the way down, both its velocity and acceleration are downward, and at the highest point both its velocity and acceleration are zero. c. Throughout the motion, the acceleration is downward, and the velocity is always in the same direction as the acceleration. d. The acceleration is downward at all points in the motion. e. The acceleration is downward at all points in the motion except that is zero at the highest point.

D

An object is moving with constant non-zero velocity. Which of the following statements about it must be true? a. A constant force is being applied to it in the direction of motion. b. A constant force is being applied to it in the direction opposite of motion. c. A constant force is being applied to it perpendicular to the direction of motion. d. The net force on the object is zero. e. Its acceleration is in the same direction as it velocity.

D

Three vectors F1, F2, and F3, each of magnitude 70 units, all act on an object as shown in the figure. The magnitude of the resultant vector acting on the object is

D) 0 units

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

D) 11 units

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 air resistance is negligible small?

D) 91 m

A rock is thrown from the upper edge of a tall cliff at some angle above the horizontal. It reaches its highest point and starts falling down. Which of the following statements about the rock's motion are true just before it hits the ground? (There could be more than one correct choice.)

D) Its horizontal velocity component is the same as it was just as it was launched.

An object moving in the +x direction experiences an acceleration of +2.0 m/s2. This means the object

D) is increasing its velocity by 2.0 m/s every second

For general projectile motion with no air resistance, the horizontal component of a projectile's velocity

D) remains a non-zero constant

True or False: If a vector's components are all negative, then the magnitude of the vector is negative.

False

0

The sum of two vectors of fixed magnitudes has its minimum magnitude when the angle between these vectors is

180

The sum of two vectors of fixed magnitudes has the greatest magnitude when the angle between these two vectors is

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.

The thrown pebble hits first The dropped pebble hits first *They hit at the same time* We cannot tell without knowing which pebble is heavier

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

True or False: The magnitude of a vector can never be less than the magnitude of any of its components

True

True

True or False: If (vector) A - (vector) B = 0, then the vectors A and B have equal magnitudes and are directed in the *same* direction.

False

True or False: If *three* vectors add to zero, they must *all* have equal magnitudes

False

True or False: If a vector pointing upward has a positive magnitude, a vector pointing downward has a negative magnitude.

is equal to 2.0 m *could be as small as 2.0 m or as large as 12 m* is equal to 12 m is equal to 8.6 m

Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. If these two vectors are added together, the magnitude of the sum...

Vectors M and N are at right angles to each other Vectors M and N point in the same direction *Vectors M and N have the same magnitudes* The magnitude of M is the negative of the magnitude of N

Vectors M and N obey the equation M + N = 0. These vectors satisfy which one of the following statements?

An elevator suspended by a vertical cable is moving downward but slowing down. The tension in the cable must be a. greater than the weight of the elevator. b. less than than the weight of the elevator. c. equal to the weight of the elevator.

a

For general projectile motion with no air resistance, the horizontal component of a projectile's acceleration a. is always zero. b. remains a non-zero constant. c. continuously increases. d. continuously decreases. e. first decreases and then increases.

a

A boy kicks a football from ground level with an initial velocity of 20 m/s at an angle of 30⁰ above the horizontal. What is the horizontal difference to the point where the football hits the ground if we neglect air resistance? a. 35 m b. 48 m c. 60 m d. 20 m e. 10 m

a. 35 m

Which of the following situations is impossible? a. An object has constant non-zero velocity and changing deceleration. b. An object has velocity directed east and acceleration directed west. c. An object has zero velocity but non-zero acceleration. d. An object has constant non-zero acceleration and changing velocity. e. An object has velocity directed east and acceleration directed east.

a. An object has constant non-zero velocity and changing deceleration.

A projectile is fired from ground level on a horizontal plain. If the initial speed of the projectile is now doubled, and we neglect air resistance, a. Its range will quadruple b. Its range will be increased by √2 c. Its range will double d. Its range will decrease by a factor of four e. Its range will be decreased by a factor of two.

a. Its range will quadruple

Suppose that an object travels from one point in space to another. Make a comparison between the magnitude of the displacement and the distance traveled by this object. a. The displacement is either less than or equal to the distance travelled. b. The displacement is always equal to the distance traveled. c. The displacement can be either greater than, smaller than, or equal to the distance travelled. d. The displacement is either greater than or equal to the distance travelled.

a. The displacement is either less than or equal to the distance travelled.

A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball as it is going up is correct? a. Both its velocity and its acceleration point upward. b. Its velocity points upward and its acceleration points downward. c. Its velocity points downward and its acceleration points upward. d. Both its velocity and its acceleration points downward.

b

For general projectile motion with no air resistance, the horizontal component of a projectile's velocity a. remains zero. b. remains a non-zero constant. c. continuously increases. d. continuously decreases. e. first decreases and then increases.

b

For general projectile motion with no air resistance, the vertical component of a projectile's acceleration a. is always zero. b. remains a non-zero constant. c. continuously increases. d. continuously decreases. e. first decreases and then increases.

b

When a 45-kg person steps on a scale in an elevator, the scale reads a steady 410 N. Which of the following statements must be true? (There could be more than one correct choice.) a. The elevator is accelerating upward at a constant rate. b. The elevator is accelerating downward at a constant rate. c. The elevator is moving upward at a constant rate. d. The elevator is moving downward at a constant rate. e. From the given information, we cannot tell if the elevator is moving up or down.

b and e

The sum of two vectors of fixed magnitudes has the greatest magnitude when the angle between these two vectors is a. 60⁰ b. 0⁰ c. 180⁰ d. 270⁰ e. 90⁰

b. 0⁰

The horizontal and vertical components of the initial velocity of a football are 16 m/s and 20 m/s, respectively. If there is no air resistance, how long does it take the football to reach the top of its trajectory. a. 5.0 s b. 2.0 s c. 3.0 s d. 4.0 s e. 1.0 s

b. 2.0 s

A ball is thrown straight up, reaches a max height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball as it is going up is correct? a. Both its velocity and its acceleration point upward. b. Its velocity points upward and its acceleration points downward. c. Its velocity points downward and its acceleration points upward. d. Both its velocity and its acceleration point downward.

b. Its velocity points upward and its acceleration points downward.

For general projectile motion with no air resistance, the vertical component of a projectile's acceleration...

is always zero *remains a non-zero constant* continuously increases continuously decreases

Under what condition is average velocity equal to the average of the object's initial and final velocity? a. The acceleration must be constantly decreasing. b. The acceleration is constant. c. This can only occur if there is no acceleration. d. This can occur only when the velocity is 0. e. The acceleration must be constantly increasing.

b. The acceleration is constant.

A ball is thrown horizontally from the top of a tower at the same instant that a stone is dropped vertically. Which object is traveling faster when it hits the level ground below if neither of them experiences any air resistance? a. It is impossible to tell because we don't know their masses. b. The ball c. The stone d. Both are travelling at the same speed

b. The ball

Which of the following statements are true about an object in 2D projectile motion with no air resistance? a. The speed of the object is 0 at the highest point. b. The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward. c. The speed of the object is constant but its velocity is not constant. d. The acceleration of the object is +g when the object is rising and -g when it is falling. e. The acceleration of the object is 0 at its highest point.

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

When a ball is thrown straight up with no air resistance, the acceleration at its highest point a. is upward b. is downward c. reverses from downward to upward d. is zero e. reverses from upward to downward

b. is downward

From the edge of a roof top you toss a green ball upwards with initial speed v0 and a blue ball downwards with the same initial speed. Air resistance is negligible. When they reach the ground below a. the green ball will be moving faster b. the two balls will have the same speed c. the blue ball will be moving faster

b. the two balls will have the same speed

A pilot drops a package from a plane flying horizontally at a constant speed. *Neglecting air resistance*, when the package hits the ground, the horizontal location of the plane will...

be directly over the package

A 4.0 kg object is moving with speed 2.0 m/s. A 1.0 kg object is moving with speed 4.0 m/s. Both objects encounter the same constant braking force, and are brought to rest. Which object travels the greater distance before stopping? a. the 4.0 kg object b. the 1.0 kg object c. Both objects travel the same distance. d. It cannot be determined from the information given.

c

A satellite is in orbit around the earth. Which one feels the greater force? a. the satellite because the earth is so much more massive b. the earth because the satellite has so little mass c. Earth and the satellite feel exactly the same force. d. It depends on the distance of the satellite from Earth.

c

A small car and a large SUV are at a stoplight. The car has a mass equal to half that of the SUV, and the SUV can produce a maximum accelerating force equal to twice that of the car. When the light turns green, both drivers push their accelerators to the floor at the same time. Which vehicle pulls ahead of the other vehicle after a few seconds? a. The car pulls ahead. b. The SUV pulls ahead. c. It is a tie.

c

If the force on an object is in the negative direction, the work it does on the object must be a. negative. b. positive. c. The work could be either positive or negative, depending on the direction the object moves.

c

Swimmers at a water park have a choice of two frictionless water slides, as shown in the figure. Although both slides drop over the same height h, slide 1 is straight while slide 2 is curved, dropping quickly at first and then leveling out. How does the speed v1 of a swimmer reaching the bottom of slide 1 compare with v2, the speed of a swimmer reaching the end of slide 2? a. v1 > v2 b. v1 < v2 c. v1 = v2 d. The heavier swimmer will have a greater speed than the lighter swimmer, no matter which slide he uses. e. No simple relationship exists between v1 and v2.

c

You throw a rock horizontally off a cliff with a speed of 20 m/s and no significant air resistance. After 2.0 seconds, the magnitude of the velocity of the rock is closest to a. 40 m/s b. 20 m/s c. 28 m/s d. 37 m/s

c. 28 m/s

An auto manufacturer advertises that their car can go "from zero to sixty in eight seconds." This is a description of what characteristic of the car's motion? a. average speed b. instantaneous speed c. average acceleration d. instantaneous acceleration e. displacement

c. average acceleration

average velocity

change in velocity divided by change in time

A ball is thrown with an initial velocity of 20 m/s at an angle of 60⁰ above the horizontal. If we can neglect air resistance, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory.

d. 10 m/s

An object starts from rest and undergoes uniform acceleration. During the first second it travels 5.0 meters. How far does it travel during the third second? a. 45 meters b. 5.0 meters c. 15 meters d. 25 meters

d. 25 meters

A ball is thrown downward from the top of a building with an initial speed of 25 m/s. It strikes the ground after 2.0 seconds. How high is the building, assuming negligible air resistance? a. 30 m b. 20 m c. 50 m d. 70 m

d. 70 m

Human reaction time is usually greater than 0.10 seconds. If your friend holds a ruler between your fingers and releases it without warning, how far can you expect the ruler to fall before you catch it, assuming negligible air resistance? a. Less than 3.0 m b. At least 9.8 cm c. At least 7.8 cm d. At least 4.9 cm

d. At least 4.9 cm

Suppose that an object is moving with a constant velocity. Which statement concerning its acceleration must be correct? a. The acceleration is constantly increasing. b. The acceleration is constantly decreasing. c. The acceleration is a constant non-zero value. d. The acceleration is equal to zero.

d. The acceleration is equal to zero.

Suppose that a car travelling to the west begins to slow down as it approaches a traffic light. Which of the following statements about its acceleration is correct? a. The acceleration is zero b. Since the car is slowing down, its acceleration must be negative. c. The acceleration is toward the west. d. The acceleration is toward the east.

d. The acceleration is toward the east.

Two objects are dropped from a bridge, an interval of 1.0 seconds apart. Air resistance is negligible. During the time that both objects continue to fall, their separation a. decreases at first, but then stays constant b. decreases c. stays constant d. increases e. increases at first, but then stays constant

d. increases

Two men, Joel and Jerry, push against a car that has stalled, trying unsuccessfully to get it moving. Jerry stops after 10 min, while Joel is able to push for 5.0 min longer. Compare the work they do on the car. a. Joel does 75% more work than Jerry. b. Joel does 50% more work than Jerry. c. Jerry does 50% more work than Joel. d. Joel does 25% more work than Jerry. e. Neither of them does any work.

e

Which of the following statements are true about an object in two-dimensional projectile motion with no air resistance? (There could be more than one correct choice.) a. The speed of the object is constant but its velocity is not constant. b. The acceleration of the object is +g when the object is rising and -g when it is falling. c. The acceleration of the object is zero at its highest point. d. The speed of the object is zero at its highest point. e. The horizontal acceleration is always zero and the vertical acceleration is always a non-zero constant downward.

e

At player kicks a soccer ball in a high arc toward the opponent's goal. A the highest point in its trajectory a. both the velocity and the acceleration of the soccer ball are zero b. the ball's acceleration is 0 but its velocity is not 0 c. the ball's velocity points downward d. the ball's acceleration points upward e. neither the ball's velocity nor its acceleration are 0

e. neither the ball's velocity nor its acceleration are 0

In order to lift a bucket of concrete, you must pull up harder on the bucket than the bucket pulls down on you

false

You pull on a crate with a rope. If the crate moves, the rope's pull on the crate must have been larger than the crate's pull on the rope, but if the crate does not move, both of these pulls must have been equal. true or false

false

You are trying to cross a river that flows toward the south with a strong current. You start out in your motorboat on the east bank, desiring to reach the west bank directly west from your starting point. You should head your motorboat...

in a general northwesterly direction