Physics Unit B Test

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

0 m/s2

A ball rolls over the edge of a table with a horizontal velocity V m/s. The height of the table is 1.6 m and the horizontal range of the ball from the base of the table is 20 m. How long does it take for the ball to hit the ground?

0.57 s

A jumper in the long-jump goes into the jump with a speed of 12m/s at an angle of 20° above the horizontal. How long is the jump in the air before returning to earth?

0.84 s

A ball is thrown horizontally with an initial velocity of 40 m/s from a height of 10 m. How long will it take for the ball to touch the ground?

1.4 seconds

A hockey puck slides of the edge of a table with an initial velocity of 20.0 m/s. The height of the table above ground is 2.00 m. How far from the edge of the table, measured along the floor, does the puck hit the floor?

12.8 m

A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0 degrees above the horizontal at a location where g=10.0 m/s2. What is the horizontal component of its velocity after 4 seconds?

130 m/s

A ball is thrown horizontally from the top of a building. What will be its vertical displacement from the top of the building 2.0 seconds after it leaves your hands?

19.6 m

A hockey puck slides of the edge of a table with an initial velocity of 20.0 m/s. The height of the table above ground is 2.0 m. What is the magnitude of the velocity of the puck just before it touches the ground?

21 m/s

The horizontal and vertical components of the initial velocity of a football are 24 m/s and 7 m/s respectively. What is the initial velocity of the football?

25 m/s

A bullet is fired with a certain velocity at an angle • above the horizontal at a location where g=10.0 m/s2. The initial x- and y- components of its velocity are 86.6 m/s and 50.0 m/s respectively. At what angle is the bullet fired above the horizontal?

30.0°

A bullet is fired from ground level with a speed of 150 m/s at an angle 30.0 degrees above the horizontal at a location where g=10.0 m/s2. What is the vertical component of its velocity after 4 seconds?

35 m/s

For which value of • is the range of a projectile fired from ground level a maximum?

45° above the horizontal

A jumper in the long-jump goes into the jump with a speed of 12 m/s at an angle of 20° above the horizontal. How far does the jumper jump?

9.4 m

For which value of • is the height of a projectile fired from ground level a maximum?

90° above the horizontal

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

Be over the bomb

Mary and Debra stand on a snow covered rood. 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°. When the snowballs reach the ground below,

Both snowballs will hit the ground with the same speed

For a projectile launched horizontally, the vertical component of a projectile's velocity

Continuously increases

Mary and Debra stand on a snow covered rood. They both throw snowballs downward, at 30° below the horizontal; Debra throws her snowball upward, at 30°. When the snowballs reach the ground below,

Debra's snowball will stay in the air longer than Mary's

Two objects are thrown vertically upwards simultaneously, one on the surface of the earth and the other on the surface of the moon. Both have an initial velocity of 20 m/s. Both objects will take the same time to reach the highest point of their trajectory.

False

Two similar objects are thrown simultaneously from the top of a building with the same speed. One is thrown vertically downward, and the other at an angle. Both objects reach the ground at the same time.

False

Two athletes jump straight up. John has twice the initial speed of Harry. Compared to Harry, John jumps

Four times as long

A monkey is sitting at the top of a tree 20 m high from the ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the person launches the food, how should the person auk the arrow containing the food?

He should aim it at the monkey

You drop a stone from a bridge to the river below. After this stone has traveled a distance, d, you drop a second stone. The distance between the two stones will always

Increase

Two objects are dropped from a bridge, an interval if 1.0 s apart. During that time that both objects continue to fall, their separation

Increases

For general projectile motion, the horizontal component of a projectile's acceleration

Is zero

A rock is thrown at some angle above the horizontal with a certain velocity. It reaches it's highest point and starts falling down. What is the velocity of the rock at the highest point in its trajectory?

It is equal to it's initial horizontal velocity

A rock is thrown from ground level at some angle above ye horizontal with a certain velocity. It reaches it's highest point and starts falling down. What is he magnitude of the velocity of the rock right before it hits the ground?

It is equal to the magnitude of its initial velocity.

If the initial speed of a projectile is doubled.

It's range will quadruple

A stone is thrown straight up. When it reached it highest point

It's velocity is zero and it's acceleration is not zero

Suppose a ball is thrown straight up, reaches a maximum height, then falls to it's initial height. Make a statement about the direction of the velocity and acceleration as the ball is going up.

It's velocity points upward and it's acceleration points downward

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. Compare the time is takes each to reach the lake below.

James and John will reach the surface of the lake at the same time.

A student 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 it's acceleration is zero

For a projectile launched horizontally, the horizontal component of a projectile's velocity

Remains a non-zero constant

For general projectile motion, the horizontal component of a projectile's velocity

Remains a non-zero constant

For general projectile motion, the vertical component of a projectile's acceleration

Remains a non-zero constant

A rock is thrown upwards at an angle of 40 degrees with respect to the horizontal. As the rock is rising in it's trajectory, the horizontal component of its velocity

Remains the same

A ball rolls off the edge of a table. The horizontal component of the ball's velocity remains constant during its entire trajectory because

The ball is not acted upon by a force in the horizontal direction

A mountain climber encounters a crevasse in an ice field. The opposite side of the crevasse is a height h lower, and is separated horizontally by a distance w. To cross the crevasse, the climber gets a running start and jumps in the horizontal direction. If the height of the crevasse increases but the width remains the same, then,

The minimum speed needed to cross the crevasse decreases

If the acceleration vector of an object is directed anti-parallel to the velocity vector,

The object is slowing down

If the acceleration vector of an object is directed parallel to the velocity vector,

The object is speeding up

If the acceleration vector of an object is directed perpendicular to the velocity vector,

The object is turning

A projectile is launched with initial velocity V0 at an angle of 30° above the horizontal. If a second projectile is launched with the same initial velocity but at angle of 60° above the horizontal.

The ranges of the two projectiles will be identical

Marcia uses a bow to shoot an arrow with initial velocity V0 of magnitude and at an angle • above the horizontal. When the arrow returns to the same height from which it started,

The speed of the arrow is again V0

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start an jumps with an initial horizontal velocity of 25 m/s. When they reach the lake below,

The splashdown speed if John is larger than that of James.

From the edge of a roof top you toss a green ball upwards with initial velocity V0 and a blue ball downward with the same initial velocity. When they reach the ground below

The two balls will have the same speed

An athlete throws a ball with a velocity of 40 m/s at an angle if 20° above the horizontal. Which of the following statements is true in this case?

The vertical component of the velocity changes sign after the ball attains it's maximum height

A ball is thrown at an angle of • above the horizontal. If there is no acceleration due to gravity the ball will follow a straight-line path.

True

A projectile is launched from ground level with a certain speed. For any range less than the maximum there are two possible launch angles that give the same range.

True

The horizontal component of the velocity of a projectile remains constant during the entire trajectory of the projectile.

True

The vertical component of the acceleration of a projectile remains constant during the entire trajectory of the projectile.

True

Two athletes jump straight up. John has twice the initial speed of Harry. Compared to Harry, John stays in the air

Twice as long