Chapter 3 Physics Smartbook
If the launch velocity is the same, which launch angle gives the maximum range?
45 degrees Reason: The range is the product of the horizontal component of the initial velocity and the time of flight. The time of flight is dependent on the vertical component of the initial velocity. This value is maximized when the vertical component of the velocity equals the horizontal component. This occurs only when the launch angle is 450.
A ball is thrown straight upwards with an initial velocity v0 = 30 m/s. The ball will reach a maximum height of m in seconds. Use g ≈ 10 m/s2 pointing downward.
45, 3
A ball that falls with an initial velocity v0 = 10 m/s will travel a distance of _____ m in 3 seconds. Assume that the acceleration of gravity is 9.8 m/s2. Round the final answer to two decimal places.
74.1 d= v0t + 1/2at^2 d= 10(3) + 1/2(9.8)(3)6^2 d= 74.1
An object is projected with an initial angle θ0 = 30° and an initial velocity v0. Identify the following that describe the motion of the object.
The object will travel horizontally equal distances in equal times. The horizontal velocity of the object is constant.
a child dropped a light pencil and a heavy book at the same time from a balcony. assuming that acceleration of gravity equals 10 m/s2, which of the following is correct? (ignore air resistance)
in three seconds, both the book and pencil will have the same speed Reason: Both the book and the pencil gain a a speed of 10 m/s each second. Therefore, in 3 seconds, both will be moving downward with a speed of 30 m/s
You are standing next to a cliff and throw a ball straight upward with an initial velocity v0 = 30 m/s. After 7 seconds, the ball will be at a height of _____ m. Use g ≈ 10 m/s2 pointing down and take the point from which you throw the ball as the reference.
-35m Reason: Use d = v0t - (1/2)at^2
Select the option that explains why Galileo rejected Aristotle's theory describing the motion of falling objects.
-Aristotle's observations did not take all relevant factors (e.g., air resistance) into account. - Galileo relied on experiments that proved Aristotle wrong.
An object of mass 1 kg is dropped from a table of height 1 m. You represent the motion by drawing velocity and acceleration vectors of the object as it falls. At 10 cm intervals away from the table, which of the following statements are true?
-At all points between the table and the ground, the acceleration vector points downward and is constant. -At any point between the table and the ground, both the acceleration and velocity vectors point in the same direction.
Fill in the blank question. A car moves to the right with an initial velocity v0 = 30 msms and an acceleration a = 5 ms2ms2 pointing to the left. After 4 seconds, the car's speed will be
10 v=v0+at v= 30+(-5)(4) v=10
A projectile is launched on the Moon with an initial angle θ, initial vertical velocity v0y = 10 m/s, and initial horizontal velocity v0x = 15 m/s. The gravitational acceleration on the moon is one-sixth of the gravitational acceleration on the earth. The projectile reaches a maximum height ymax = 6.3 m. The horizontal velocity at that point is equal to m/s.
15 m/s
Two balls are thrown at the same time. One up with initial velocity v0,1 = 30 m/s and the other down with initial velocity v0,2 = -30 m/s. After 2 seconds, the difference (v1 −v2) of their velocities will be equal to _____ m/s (assume that neither ball has hit the ground yet).
60 30-(-30)= 60
A child drops a soda can from a balcony. The can gains a speed of --- m/s in 8 seconds. (Assume that acceleration of gravity equals 10 m/s2.)
80 m/s
If the launch velocity is the same, which launch angle gives the highest peak?
85 degrees
The gravitational acceleration near Earth is constant and is equal to
9.8 m/s2 980 cm/s2
For a book sitting on a table, the acceleration of gravity is equal to--- m/s2
9.8 or 10
Select all motions that involve acceleration.
A car negotiating a curved road, moving with a constant speed. A car speeding up in the positive direction. A car slowing down in the negative direction.
For an object moving with a constant acceleration, select all the answers that would represent the motion.
A graph showing how the velocity changes with time is a straight line with a non-zero slope. A graph showing how the position changes with time is a parabola.
Three balls are projected horizontally from a table that is 1.0 m high with initial horizontal velocities v1 = 10 msms, v2 = 20 msms, and v3 = 30 msms. Select all the correct statements about the motion of the balls.
After falling 1 m, the ball with velocity v3 will have traveled horizontally three times as far as the ball with velocity v1. All the balls will have the same vertical velocity right before they hit the ground. All the balls will hit the ground at the same time
Galileo used an inclined plane to slow down the falling motion so that he could measure the acceleration due to gravity. What was his rationale for using the inclined plane?
Along an inclined plane, only part of gravity acts on the object in its direction of motion.
If an object is dropped from a height of 10 m, which of the following statements are true?
At any point during the fall, neither the velocity nor acceleration depends on the mass of the object.
One ball is thrown straight upward with an initial velocity v0. At the same time, a second ball is launched from the same place with an initial angle θ = 30° and the initial velocity v1. Which of the following is correct?
Both balls will reach the same height if the vertical component of v1 is equal to v0. If the initial angle θ is increased, you will have to decrease the initial velocity to reach the same height.
True or false: Two cars are moving in the same direction, one with velocity v1 = 20 ms�� and the other with velocity v2 = 30 ms��. This means that the faster car has a larger acceleration.
False Reason: B/c there is no change in velocity (velocity is constant in this process), therefore, acceleration is zero.
A ball rolls off a table that is 3 meters high with a horizontal velocity v = 10 msms. It hits the ground after 0.78 s. Match the measured quantity with the correct value.
Final horizontal speed: 10 m/s. Initial vertical speed: 0 m/s. Final vertical speed: 7.67 m/s.
A sailing boat, moving with a positive initial velocity v0 against a constant strong current suddenly experiences motor failure. Which graph best shows how the velocity of the boat changes with time, after the failure?
Graph 2
For objects in free fall, select all the answers that are correct.
Gravitational acceleration is the same for all masses. Gravitational acceleration always points down.
Along the trajectory of a projectile, the ----velocity remains constant, because there is no---- in that direction.
Horizontal Acceleration
Two cars are moving in the same direction. They have accelerations a1 = 4.0 ms2ms2 and a2 = 6.0 ms2ms2. Based on this information, select the correct answers.
If both cars started from rest, one car always moves 1.5 times faster than the other. The car with a larger acceleration has a larger increase in velocity in the same period of time.
An object thrown down with initial velocity v0 hits the ground after 4 seconds. Select all the options that are correct.
If v0 is increased, the time it takes to hit the ground would decrease. The object will hit the ground earlier than another object dropped from the same height. A graph showing how far the object travels with time will be a parabola.
Two projectiles are launched from the same initial elevation and reach the same peak elevation, but projectile A travels a larger horizontal distance than projectile B. Match the quantity for A with the relationship to B's quantity. Instructions
Initial velocity of A: Greater than B. Time spent in the air by A: Same as B. Initial launch angle of A: Less than B.
Whether you throw a ball upward or downward
Its acceleration is always pointing downward.
For a projectile thrown at some angle greater than zero but less than ninety degrees, at a given moment, which of the following could be true about its velocity? You may choose more than one.
Its velocity could be exclusively horizontal. Its velocity could have both vertical and horizontal components.
the graph shows how the velocities of four objects change with time. select the motions that involve acceleration.
Object 4 between 2 seconds and 13 seconds Object 2 between 12 seconds and 18 seconds Object 1 between 2 seconds and 6 seconds
Assume that an object is moving in the positive direction. Match the correct pairs.
Slowing down -- involves negative acceleration. Speeding up-- involves positive acceleration. Moving with a constant speed along a straight line-- involves zero acceleration.
A dropped ball, starting from rest, accelerates downward. Select all the answers that describe its motion.
The equation d = 1/2 at^2 can be used to calculate the distance traveled by the ball . The ball falls faster during the fourth second than it did during the first second
A hunter with a blowgun saw a monkey hanging in a tree. The hunter aimed at the monkey and fired his blowgun at the same instant the monkey released its grip on the branch. Which of the following is correct?
The hunter will hit the monkey provided the distance to the branch is not too great.
Assuming the upwards direction to be positive, match the motion of each object with the corresponding graph. Note that the vertical axis can be either velocity or distance, you have to decide which. Instructions
Velocity as a function of time of an object thrown straight upward: Object 1 Position as a function of time of an object thrown straight upward: Object 2 Position as a function of time of an object thrown straight downward: Object 3 Velocity as a function of time of an object thrown straight downward: Object 4
a ball is projected horizontally from a table that is 1 m high with initial velocity v0 = 10 ms. at the time it hits the ground, 0.45 s after being launched, the ball will have moved horizontally a distance x = ___ m. (round your answer to the tenths place.)
dhorizontal= v0t 10(0.45) x=4.5
The hunter aimed at the monkey with his blowgun and fired at the same instant as the monkey released its grip on the branch. The hunter will hit the monkey
regardless of whether the monkey was light or heavy. Reason: Mass does not appear anywhere in the kinematic equations. Therefore, independent of mass, both the monkey and the projectile fall at the same rate (due to gravity), spend the same amount of time in the air, and travel the same vertical distance.
A bullet is shot with an initial velocity v0 and an initial angle θ0 = 45°. Select the correct relationship between the initial components.
v0x = v0y Reason: At 45°, the vertical and horizontal components of a vector are equal.
An object is thrown straight downward with an initial velocity v0 = 35 ms��. Taking the down direction to be positive, the velocity of the particle after 5 seconds will be ms��. Notice that by saying the initial velocity in the downward direction is 35 m/s, we have chosen the downward direction as positive. If needed, use g = 10 m/s2 as the approximate value for the acceleration due to gravity.
v= v0+at v= 35+(10)(5) V= 85
Object B is thrown straight up with an initial velocity v0. Taking the upward direction as positive, select all the statements that describe the motion. (Ignore air resistance.)
when the object returns to its final position, its velocity is --v0 it takes the same time to go up to its maximum height as it takes to come down to the original position