Physics Chapter 2
A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, and then 1.0 km north to return to its starting point. This trip takes 45 min. What was the bear's average velocity?
0.00 km/h
A car is traveling north at 17.7 m/s After 12 s its velocity is 14.1 m/s in the same direction. Find the magnitude and direction of the car's average acceleration.
0.30 m/s^2 , south
The graph in the figure shows the position of a particle as it travels along the x-axis. What is the magnitude of the average velocity of the particle between t = 1.0 s and t = 4.0 s?
0.67 m/s
An airplane needs to reach a forward velocity of 203.0 km/h to take off. On a 2000-m runway, what is the minimum uniform acceleration necessary for the plane to take flight if it starts from rest?
0.79 m/s^2
A laser is thrown upward with a speed of 12 m/s on the surface of planet X where the acceleration due to gravity is 1.5 m/s^2 and there is no atmosphere. How long does it take for the laser to reach the maximum height?
8.0 s
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?
80 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?
88 km/h
A motorist travels 160 km at 80 km/h and 160 km at 100 km/h. What is the average speed of the motorist for this trip?
89 km/h
Under what condition is average velocity equal to the average of the object's initial and final velocity?
The acceleration is constant
Suppose that an object is moving with a constant velocity. Which statement concerning its acceleration must be correct?
The acceleration is equal to zero.
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.
The displacement is either less than or equal to the distance traveled.
Two objects are dropped from a bridge, an interval of 1.0 s apart. Air resistance is negligible. During the time that both objects continue to fall, their separation
increases
When a ball is thrown straight up with no air resistance, the acceleration at its highest point
is downward
An object moving in the +x direction experiences an acceleration of +2.0 m/s^2 . This means the object
is increasing its velocity by 2.0 m/s every second.
You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be
less than 70 km/h.
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?
3.95 m/s
A car is moving with a constant acceleration. At time t = 5.0 s its velocity is 8.0 m/s in the forward direction, and at time t = 8.0 s its velocity is 12.0 m/s forward. What is the distance traveled in that interval of time?
30 m
To determine the height of a bridge above the water, a person drops a stone and measures the time it takes for it to hit the water. If the time is 2.3 s, what is the height of the bridge? Neglect air resistance.
32 m
A polar bear starts at the North Pole. It travels 1.0 km south, then 1.0 km east, and then 1.0 km north to return to its starting point. This trip takes 45 min. What was the bear's average speed?
4.0 km/h
A ball is thrown downward in the absence of air resistance. After it has been released, which statement(s) concerning its acceleration is correct? (There could be more than one correct choice.)
Its acceleration is constant.
A jet plane is launched from a catapult on an aircraft carrier. In 2.0 s it reaches a speed of 42 m/s at the end of the catapult. Assuming the acceleration is constant, how far did it travel during those 2.0 s?
42 m
What must be your average speed in order to travel 350 km in 5.15 h?
68.0 km/h
Which of the following situations is impossible?
An object has constant non-zero velocity and changing acceleration.
A ball is thrown upward at a velocity of 19.6 m/s. What is its velocity after 3.0 s, assuming negligible air resistance?
9.8 m/s downward
An airplane starts from rest and accelerates at a constant 10.8 m/s 2 . What is its speed at the end of a 400 m-long runway?
93.0 m/s
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?
The acceleration is downward at all points in the motion.
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 velocity of the stone as a function of time?
(graph slopes down)
A runner runs around a track consisting of two parallel lines 96 m long connected at the ends by two semicircles with a radius of 49 m. She completes one lap in 100 seconds. What is her average velocity?
0 m/s
If the acceleration of an object is zero, then that object cannot be moving.
False
When is the average velocity of an object equal to the instantaneous velocity?
when the velocity is constant
Suppose that a car traveling to the east (+x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration must be correct?
Its acceleration is in the -x direction
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?
Its acceleration is positive.
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?
Its velocity points upward and its acceleration points downward.
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?
(graph is a little above mid-line and constant)
A certain test car can go from rest to 32.0 m/s in 3.88 s. The same car can come to a full stop from that speed in 4.14 s. What is the ratio of the magnitude of the starting acceleration to the stopping acceleration?
1.07
The graph in the figure shows the position of a particle as it travels along the x-axis. What is the magnitude of the average speed of the particle between t = 1.0 s and t = 4.0 s?
1.3 m/s
The graph in the figure shows the velocity of a particle as it travels along the x-axis. What is the magnitude of the average acceleration of the particle between t = 1.0 s and t = 4.0 s?
1.7 m/s^2
A cart starts from rest and accelerates uniformly at 4.0 m/s 2 for 5.0 s. It next maintains the velocity it has reached for 10 s. Then it slows down at a steady rate of 2.0 m/s^2 for 4.0 s. What is the final speed of the car?
12 m/s
An instrument is thrown upward with a speed of 15 m/s on the surface of planet X where the acceleration due to gravity is 2.5 m/s^2 and there is no atmosphere. How long does it take for the instrument to return to where it was thrown?
12 s
An astronaut stands by the rim of a crater on the Moon, where the acceleration of gravity is 1.62 m/s^2 and there is no air. To determine the depth of the crater, she drops a rock and measures the time it takes for it to hit the bottom. If the depth of the crater is 120 m, how long does it take for the rock to fall to the bottom of the crater?
12.2 s
A hammer is thrown upward with a speed of 14 m/s on the surface of planet X where the acceleration due to gravity is 3.5 m/s^2 and there is no atmosphere. What is the speed of the hammer after 8.0 s?
14 m/s
A car is moving with a speed of 32.0 m/s. The driver sees an accident ahead and slams on the brakes, causing the car to slow down with a uniform acceleration of magnitude 3.50 m/s 2 . How far does the car travel after the driver put on the brakes until it comes to a stop?
146 m
A stone is thrown with an initial upward velocity of 7.0 m/s and experiences negligible air resistance. If we take upward as the positive direction, what is the velocity of the stone after 0.50 s?
2.1 m/s
Acceleration is sometimes expressed in multiples of g, where g= 9.8 m/s^2 is the acceleration of an object due to the earth's gravity. In a car crash, the car's forward velocity may go from 29 m/s to 0 m/s in 0.15 s. How many g's are experienced, on average, by the driver?
20 g
An astronaut stands by the rim of a crater on the Moon, where the acceleration of gravity is 1.62 m/s^2 and there is no air. To determine the depth of the crater, she drops a rock and measures the time it takes for it to hit the bottom. If the time is 6.3 s, what is the depth of the crater?
26 m
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.
26.0 m, 4.0 m
Starting from rest, a dragster travels a straight 1/4 mi racetrack in 6.70 s with constant acceleration. What is its velocity when it crosses the finish line?
269 mi/h
A car starts from rest and accelerates at a steady 6.00 m/s^2. How far does it travel in the first 3.00 s?
27.0 m
An airplane travels at 300 mi/h south for 2.00 h and then at 250 mi/h north for 750 miles. What is the average speed for the trip?
270 mi/h
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 20 ms. What is the average acceleration of the ball during the collision with the wall?
2800 m/s^2
The graph in the figure shows the position of a particle as it travels along the x-axis. At what value of t is the speed of the particle equal to 0 m/s?
3 s
To determine the height of a bridge above the water, a person drops a stone and measures the time it takes for it to hit the water. If the height of the bridge is 41 m, how long will it take for the stone to hit the water? Neglect air resistance.
3.2 s
An airplane increases its speed at the average rate of 15 m/s^2 . How much time does it take to increase its speed from 100 m/s to 160 m/s?
4.0 s
A car initially traveling at 60 km/h accelerates at a constant rate of 2.0 m/s^2 . How much time is required for the car to reach a speed of 90 km/h?
4.2 s
A car travels at 15 m/s for 10 s. It then speeds up with a constant acceleration of 2.0 m/s^2 for 15 s. At the end of this time, what is its velocity?
45 m/s
A laser is thrown upward with a speed of 12 m/s on the surface of planet X where the acceleration due to gravity is 1.5 m/s^2 and there is no atmosphere. What is the maximum height reached by the laser?
48 m
A bullet shot straight up returns to its starting point in 10 s. What is the initial speed of the bullet, assuming negligible air resistance?
49 m/s
A runner runs around a track consisting of two parallel lines 96 m long connected at the ends by two semicircles with a radius of 49 m. She completes one lap in 100 seconds. What is her average speed?
5.0 m/s
A cart with an initial velocity of 5.0 m/s to the right experiences a constant acceleration of 2.0 m/s 2to the right. What is the cart's displacement during the first 6.0 s of this motion?
66 m
A car accelerates from 5.0 m/s to 21 m/s at a constant rate of 3.0 m/s^2 How far does it travel while accelerating?
69 m
A ball is thrown straight up with a speed of 36 m/s. How long does it take to return to its starting point, assuming negligible air resistance?
7.3 s
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 s. How high is the building, assuming negligible air resistance?
70 m
Human reaction time is usually greater than 0.10 s. 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?
At least 4.9 cm
A racing car accelerates uniformly from rest along a straight track. This track has markers spaced at equal distances along it from the start, as shown in the figure. The car reaches a speed of 140 km/h as it passes marker 2
Before marker 1
If the instantaneous velocity of an object is zero, then that object cannot be accelerating.
False
If the velocity of an object is zero at some point, then its acceleration must also be zero at that point.
False
The motions of a car and a truck along a straight road are represented by the velocity-time graphs in the figure. The two vehicles are initially alongside each other at time t = 0.
The truck will have traveled further than the car.
Brick A is dropped from the top of a building. Brick B is thrown straight down from the same building, and neither one experiences appreciable air resistance. Which statement about their accelerations is correct?
The two bricks have exactly the same acceleration
Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? Neglect air resistance.
They are traveling at the same speed.
Consider a car that travels between points A and B. The car's average speed can be greater than the magnitude of its average velocity, but the magnitude of its average velocity can never be greater than its average speed.
True
A 10-kg rock and a 20-kg rock are dropped at the same time and experience no significant air resistance. If the 10-kg rock falls with acceleration a, what is the acceleration of the 20-kg rock?
a
An object is moving with constant non-zero velocity in the +x direction. The velocity versus time graph of this object is
a horizontal straight line
An object is moving with constant non-zero acceleration in the +x direction. The position versus time graph of this object is
a parabolic curve
An object is moving with constant non-zero acceleration in the +x direction. The velocity versus time graph of this object is
a straight line making an angle with the time axis.
An object is moving with constant non-zero velocity in the +x direction. The position versus time graph of this object is
a straight line making an angle with the time axis.
Which of the following graphs represent an object at rest? (There could be more than one correct choice.)
graph a
The slope of a velocity versus time graph gives
acceleration
If the position versus time graph of an object is a horizontal line, the object is
at rest
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?
average acceleration
A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. If the 10-kg rock reaches a maximum height h, what maximum height will the 20-kg ball reach?
h
The motion of a particle is described in the velocity vs. time graph shown in the figure. Over the nine-second interval shown, we can say that the speed of the particle
decreases and then increases.
Suppose a ball is thrown straight up and experiences no appreciable air resistance. What is its acceleration just before it reaches its highest point?
exactly g
If the velocity versus time graph of an object is a straight line making an angle up with the time axis, the object is
moving with constant non-zero acceleration
If the velocity versus time graph of an object is a horizontal line, the object is
moving with zero acceleration
Ball A is dropped from the top of a building. One second later, ball B is dropped from the same building. Neglect air resistance. As time progresses, the difference in their speeds
remains constant
A 10-kg rock and 20-kg rock are dropped from the same height and experience no significant air resistance. If it takes the 20-kg rock a time T to reach the ground, what time will it take the 10-kg rock to reach the ground?
t
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
the two balls will have the same speed.
The slope of a position versus time graph gives
velocity.