Physics 101 Exam 2

You apply a force in the x-direction of 20 N on a block that has a mass of 10 kg. If no other forces act on the block, what is its acceleration?

2 m/s^2

A force F acts on mass m1 giving acceleration a1. The same force acts on a different mass m2 giving acceleration a2 = 2a1. If m1 and m2 are glued together and the same force F acts on this combination, what is the resulting acceleration?

2/3 a 1

A car travels a distance (x) at acceleration (a) and does work (W). If the car travels a distance 2x at the same acceleration, what is the work it has done?

2W

You push an object of mass M with a force F and cause the object to reach a speed v in a certain time. If you apply the same force to an object with 1mass 2M, what velocity does it reach in that same time?

2v

You push an object of mass M initially at rest with a force F and cause the object to travel a distance x in a certain time. If you apply twice the force (2F), what distance does it travel in the same time?

2x

You push on a mass with a certain force, and the mass accelerates at 1 m/s2. With the same force, you push on a second mass. The acceleration of the second mass is 3 m/s2. Now, you stick the 2 masses together and push on them with the same force. What is the acceleration of the 2 masses?

3/4 m/s^2

A karate chop delivers a force of 3000 N to a board that breaks. The force that the board exerts on the hand during this event is

3000 N

For what angle is it possible that the x- and y-components are equal? I. 45 degrees II. 30 degrees III. 90 degrees IV. 60 degrees

45 degrees ONLY

For the two-dimensional motion of a projectile that begins and ends at the same height, all of the following apply EXCEPT (false): a. the y-component of the velocity changes direction during flight b. the y-component of the acceleration is always negative c. the maximum speed is at the top of the trajectory d. the time in flight is determined by the y-component of the velocity

C. the max speed is at the top of the trajectory

An object slides to the right on a horizontal surface. Which of these statements about the frictional force is true? I. The frictional force is to the left II. The frictional force is only dependent on the weight of the object III. The frictional force would decrease if the mass of the object was less IV. The frictional force is dependent on the speed of the object.

I & III I. the frictional force is to the left III. the frictional force would decrease if the mass of the object was less

Which is larger: I. the gravitational force exerted by the Earth on the Moon II. the gravitational force exerted by the Moon on the Earth

I and II are the same

You are shooting a projectile with a speed of 50 m/s and an angle of 55 degrees. What can you do to increase the vertical range of the projectile? I. Increase the initial angle II. Decrease the initial angle III. Increase the initial speed IV. Decrease the initial speed

I. Increase the initial angle III. Increase the initial speed

An object slides down an inclined plane as in this figure. A frictional force acts upon the block. Which of these statements is true? I. The frictional force acts in a direction up the inclined plane II. The frictional force will decrease as the block speeds up III. The frictional force will decrease if ϴ increases IV. The blocks speed will decrease as it moves down the inclined plane

I. The frictional force acts in a direction up the inclined plane III. The frictional force will decrease if ϴ increases

An object slides down an inclined plane as in this figure. A frictional force acts upon the block. Which of these statements is true? I. The frictional force is up the inclined plane II. The frictional force depends on the mass of the object III. If θ increases for this moving object, the frictional force will always decrease IV. The frictional force is dependent on the speed of the object.

I. The frictional force is up the inclined plane II. The frictional force depends on the mass of the object III. If θ increases for this moving object, the frictional force will always decrease

An object slides down an inclined plane as in this figure. A frictional force acts upon the block. Which of these statements is true? I. The frictional force will increase if the mass is bigger II. The block accelerates at a rate faster than g III. The frictional force acts in a direction down the inclined plane IV. The frictional force will decrease as the blocks speed increases

I. The frictional force will increase if the mass is bigger

A soccer ball is kicked with an initial speed and at an angle θ. Which of the following statements is true? I. The magnitude of the vertical component of the velocity is the greatest at the beginning and end of the trajectory II. The vertical component of the velocity is zero at the top of the trajectory III. The acceleration is zero at the top of the trajectory IV. The vertical component of the velocity is constant throughout the trajectory

I. The magnitude of the vertical component of the velocity is the greatest at the beginning and end of the trajectory II. The vertical component of the velocity is zero at the top of the trajectory

Which of these statements is true for an object in projectile motion? I. The x-component of the acceleration is zero II. the y-component of the velocity is zero at the top of the trajectory III. The magnitude of the x-velocity is greatest at the beginning IV. The acceleration in the y-direction at the top of the trajectory is zero

I. The x-component of the acceleration is zero II. the y-component of the velocity is zero at the top of the trajectory

An object is moving across a frictionless surface with constant velocity. Which of these statements accurately describe its motion: I. Its acceleration is zero II. The object will gradually slow down III. If the object had more mass, it would slow down more quickly IV. The object has no forces acting upon it

I. its acceleration is zero

A soccer ball is kicked with an initial speed and at an angle θ. Which of the following statements is true? I. The initial horizontal component of the velocity is equal to the final horizontal component of the velocity II. The acceleration is zero at the top of the soccer ball's trajectory III. The horizontal component of the velocity is maximum at the top of the soccer ball's trajectory IV. The initial horizontal component of the velocity is equal to the initial vertical component of the velocity.

I. the initial horizontal component of the velocity is equal to the final horizontal component of the velocity

Two shells are fired simultaneously from the same battleship at two targets. The shells follow the trajectories shown here. Which of the following statements about the shells' trajectory must be true? I. They have different angles II. They have different initial speeds III. Shell #1 is in flight for more time than shell #2.

I. they have different angles

Which of these statements about the normal force are true? I. The normal force is always equal to the weight II. The normal force always acts in a direction perpendicular to the surface III. An object must make contact with a surface in order for the normal force to be present IV. The normal force is measured in Newtons

II. The normal force always acts in a direction perpendicular to the surface III. An object must make contact with a surface in order for the normal force to be present IV. Normal force is measured in Newtons

For the two-dimensional motion of a projectile that begins and ends at the same height, all of the following apply EXCEPT: I. The maximum height occurs at the midpoint of the flight II. The time of flight to half the maximum height is equal to 1/4 the total time of flight III. The path is a parabola IV. The maximum range occurs when the launch angle is 45°.

II. the time of flight to half the max height is equal to 1/4 the total time of flight

Which of these are vector quantities? I. mass II. distance III. velocity IV. acceleration

III & IV velocity & acceleration

A bullet shot horizontally from a gun: I. Ttravels in a straight line II. strikes the ground much sooner than one dropped from the same point at the same instant III. Strikes the ground much later than one dropped vertically from the same point at the same instant IV. Strikes the ground at approximately the same time as one dropped vertically from the same point at the same instant V. Never strikes the ground

IV. Strikes the ground at approximately the same time as one dropped vertically from the same point at the same instant

Consider a block that is at rest on an inclined plane. The only forces acting on the block are the frictional, normal, and gravitational forces. Which of these statements best describe the normal force acting on the block?

N < mg

The fact that a dime pulls upward on the Earth with a force equal to the weight of the dime is an example of

Newton's third law

A soccer ball is kicked with an initial speed at an angle ϴ. Which of the following statements is true? I. The velocity of the ball at the top is zero II. The horizontal component of the velocity is greatest at the beginning III. The acceleration of the ball is positive during the second half of the trajectory IV. The balls speed increases as it travels upwards

None of these are correct

Two objects, A and B, experience the same net force. Object A has twice the mass of object B. Object Therefore, ...

Object A accelerates at one-half the rate of Object B

Which of these statements about the coefficients of friction is true?

Us > Uk

Antilock brakes keep the car wheels from locking up when you stop your car. Why does this help the car slow down?

Us > Uk so static friction is better

Which of these is true when the height of a projectile is at its maximum? I. Vx = zero II. Vo = maximum III. Vy = zero IV. Vy = maximum

Vy = zero

An elevator goes downward at a constant acceleration. What is the relationship between the weight of the object (W) and the normal force on the block (N)?

W > N

You have three equal masses, each with mass m. You exert a force, F, on one of the masses and get an acceleration a. Now, you combine the three masses and exert the same force (F) on them. What is the acceleration of this combined mass?

a/3

Newton's Second Law is known as the law of

acceleration

A projectile is launched from the ground at an angle of 30 degrees. At what point in its trajectory does this projectile have the LEAST SPEED?

at the highest point

For the two-dimensional motion of a projectile that begins and ends at the same height, all of the following apply EXCEPT, a. the time for the projectile to ascend is exactly the same as the time to descend b. the minimum speed of the projectile is just after launch c. the x-velocity of the projectile is unchanging d. the acceleration for the projectile, in both the x- and y-directions, does not change

b. the minimum speed of the projectile is just after launch

You are in a plane and want to drop a relief package to people below. Where do you release the package?

before you get to the people

From the same height and the same time, one ball is dropped and another is fired horizontally. Which on will hit the ground first?

both

Two objects are in freefall. Mass #1 experiences a gravitational force of 20 N. Mass #2 experiences a gravitational force of 30 N. Which has the larger acceleration?

both have the same acceleration

A hunter is shooting at a target that is falling vertically. When he shoots, where should he aim?

directly at the target

A basketball is shot from a free-throw range. At some point prior to the top of the basketball's trajectory, its acceleration is:

equal to the acceleration due to gravity

A basketball is shot from a free-throw range. At the top of the basketball's trajectory, its acceleration is:

equal to the acceleration due to gravity

A pilot drops a package of food and water supplies from a plane that is flying horizontally at constant speed. When the package reaches the ground, the plane's horizontal position relative to the package

is directly above the package

A cart is on a horizontal frictionless table. Once the cart has been pushed and released, what will happen to it?

it will continue at a constant velocity

Which of these make up the basic SI units of the newton?

kgm ----- s2

Which of these is another name for Newton's first law?

law of inertia

Which of these is the basic SI unit for work?

m^2 kg -------- s^2

Two objects, A and B, experience the same net force. Object A accelerates at twice the rate of object B. Therefore the:

mass of A is half that of the mass of B

A large truck runs into a small car. Which exerts the larger force on the other?

neither, they both exert the same force

You put your book on the bus seat next to you. When the bus stops suddenly, the book slides forward off the seat. Why?

no net force acted on it

Two forces act on a body. One force pushes to the north; another pushes with equal magnitude to the west. What direction does the body accelerate?

northwest

The force due to friction of an object...

opposed the direction of motion

Given that A + B = C, and that |A|^2 + |B|^2 =|C|^2, how are vectors A and B oriented with respect to each other?

perpendicular

The normal force on an object is always:

perpendicular to the surface on which the object sits

You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will:

remain vertically under the plane while falling

The inertia of a body tends to cause the body to:

resist any change in its motion

Two shells are fired simultaneously from the same battleship at two targets. The shells follow the trajectories shown here. Which target will be hit first?

target 1 (the farther one with the lower angle)

You have an object with a mass 'm,' and you exert a force 'F' on it to give it an acceleration 'a.' If you make the mass smaller, what happens to the acceleration?

the acceleration increases

A cart is being pulled along a horizontal track by an external force and accelerating. A cannon on the cart fires straight upwards. After it is fired, what happens to the ball?

the cannonball falls behind the cart

You run out of gas. You and your friends have to push your car out of the road. Which of these statements best explain why it is difficult to move the car?

the car has a lot of mass

A 2000kg car is sitting at rest in a parking lot. A bike and rider with a total mass of 60 kg are travelling along a road at 10km/h . Which system has more inertia? Why?

the car has more inertia because its mass is greater than the mass of the bike

From the same height and at the same time, one ball is fired horizontally and another ball is dropped. Which one will have the LARGER SPEED when it hits the ground?

the fired ball

An object is dropped out of an airplane. It falls and eventually reaches a constant speed (terminal velocity). After the object reaches terminal velocity, which of the following statements is true?

the force of air resistance is equal to the weight of the object

Two objects, A and B, experience the same acceleration. However, object A has twice the mass of object B. Therefore, ...

the force on object A is twice the force on object B

Two objects, A and B, experience the same net force. Object A accelerates at half the rate of object B. Therefore the

the mass of A is twice that of the mass of B

An object is moving at a constant velocity. Which statement is always TRUE?

the net force on the object is zero

An object is moving at constant velocity. Which statement is always true?

the net force on the object is zero

A block sits on an inclined plane. What happens to the normal force as the angle of the inclined plane increases?

the normal force decreases

You fire a projectile from ground level and over level ground. If you doubled the horizontal component of its initial velocity, how much more time would it take for a projectile to hit the ground?

the time to reach the ground would remain the same since the vertical component is unchanged

A person is in freefall. How doe the person perceive their weight?

they feel lighter

Consider projectiles that follow the paths shown in this figure. Is it possible that all three projectiles had the same initial speed?

yes; all three could have the same speed

A hockey puck slides on the ice at constant velocity. What is the net force acting on the puck?

zero