# Physics 203A - Final Exam

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Physics 203A - Final Exam

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### A ball is thrown vertically upward and then comes back down. During the ball's flight up and down, its velocity and acceleration vectors are A) always in opposite directions. B) always in the same direction. C) first in opposite directions and then in the same direction. D) first in the same direction and then in opposite directions

first in opposite directions and then in the same direction.

True

### Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different masses and different initial velocities. Which one will strike the plane first? A) the fastest one B) the slowest one C) the heaviest one D) the lightest one E) They strike the plane at the same time.

They strike the plane at the same time.

2.5

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True

### A cyclist is riding up a hill having a constant slope of 30º with respect to the horizon at a constant speed (in a straight line). Which statement is true? A) The net force on the bike (due to gravity, the normal force, and friction) is zero. B) The net force on the bike (due to gravity, the normal force, and friction) is in the direction of motion. C) The net force on the bike (due to gravity, etc...)is in the opposite direction of motion.

The net force on the bike (due to gravity, the normal force, and friction) is zero.

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True

### If you stood on a planet having a mass four times higher than Earth's mass, and a radius two times longer than Earth's radius, you would weigh A) the same as you do on Earth. B) two times more than you do on Earth. C) two times less than you do on Earth. D) four times more than you do on Earth

the same as you do on Earth.

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False

False

False

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False

### A wooden block contains some nails so that its density is exactly equal to that of water. If it is placed in a tank of water and released from rest when it is completely submerged, it will A) rise to the surface. B) sink to the bottom. C) remain where it is released

remain where it is released

### The Bernoulli effect is responsible for the lift force on an airplane wing. Wings must therefore be designed so as to insure that: A) air molecules will be deflected downward when they hit the wing. B) air molecules will be deflected upward when they hit the wing. C) air molecules move more rapidly past the upper surface of the wing than past the lower surface. D) air molecules move more rapidly past the lower surface of the wing than past the upper surface

air molecules move more rapidly past the upper surface of the wing than past the lower surface.

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### While in flight, how do the x and y components of the velocity vector of the ball compare at the points B and C? A) The velocity components are non-zero at B and zero at C. B) The x components are the same; the y component at C is zero m/s. C) The x components are the same; the y component has a larger magnitude at C than at B. D) The x component is larger at C than at B; the y component at B points up while at C, it points downward.

The x components are the same; the y component at C is zero m/s.

### Which of the following ideas is true about projectile motion with no air drag? A) v^2x + v^2y = constant. B) The acceleration is +g when the object is rising and -g when falling. C) The total velocity of the object is zero at the point of maximum elevation. D) The horizontal motion is independent of the vertical motion

The horizontal motion is independent of the vertical motion

### Two bullets are fired simultaneously parallel to a horizontal plane. The bullets have different masses and different initial velocities. Which one will strike the plane first? A) the fastest one B) the slowest one C) the heaviest one D) the lightest one E) They strike the plane at the same time.

They strike the plane at the same time.

### Which one of the following statements concerning kinetic energy is true? A) Kinetic energy can be measured in watts. B) Kinetic energy is always equal to the potential energy. C) Kinetic energy is always positive. D) Kinetic energy is a quantitative measure of inertia

Kinetic energy is always positive.

False

### A block is at rest on a rough incline as shown The frictional force acting on the block, along the incline, is A) zero. B) equal to the weight of the block. C) greater than the weight of the block. D) less than the weight of the block.

less than the weight of the block.

Inertia

### A rock of weight 2.0-N slides on a frictionless inclined plane. Which one of the following statements is true concerning the normal force that the plane exerts on the rock? A) The normal force is zero newtons. B) The normal force is 2.0 N. C) The normal force is less than 2.0 N, but greater

The normal force is less than 2.0 N, but greater than zero newtons.

### A rock is suspended from a string; and it accelerates downward. Which one of the following statements concerning the tension in the string is true? A) The tension points downward. B) The tension is less than the weight of the rock. C) The tension is equal to the weight of the rock. D) The tension is greater than the weight of the rock.

The tension is less than the weight of the rock.

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### A bicyclist is riding at a constant speed along a straight-line path. The rider throws a ball straight up to a height a few meters above her head. Ignoring air resistance, where will the ball land? a. behind the rider b. in front of the rider c. in the same hand that threw the ball d. in the opposite hand to the one that threw it e. This cannot be determined without knowing

in the same hand that threw the ball

### A baseball is hit upward and travels along a parabolic arc before it strikes the ground. Which one of the following statements is necessarily true? a. The acceleration of the ball decreases as the ball moves upward. b. The velocity of the ball is zero m/s when the ball is at the highest point in the arc. c. The acceleration of the ball is zero m/s2 when the ball is at the highest point in the arc. d. The x-component of the velocity of the ball is the same throughout the ball's flight. e. The velocity of the ball

The x-component of the velocity of the ball is the same
throughout the ball's flight.

### A spring-loaded gun is aimed horizontally and is used to launch identical balls with different initial speeds. The gun is at a fixed position above the floor. The balls are fired one at a time. If the speed of the second ball fired is twice the speed of the first ball fired, how is the horizontal range (denoted R in the figure) affected? a. The range for both balls will be the same. b. The range of the second ball will be half as much as that of the first ball. c. The range of the second ball will be twice as large as that of the first ball. d. The range of the second ball is about 1.4 times larger than that of the first ball. e. The range of the second ball will be smaller than that of the first ball by a factor of 1.4.

The range of the second ball will be twice as large as that
of the first ball.

### True or False? In a collision between a huge SUV and a small compact car, the SUV exerts a larger force on the compact than the compact exerts on the SUV.

False
For every action there is a reaction, equal in magnitude and opposite in direction. According to the third law of mechanics the compact car will react with the same force.

True

### True or False? A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point down the ramp.

False
Constant velocity means zero acceleration, therefore no net force despite the fact that the crate is moving. Moving object does not mean there is a net force. That would be Aristotle's thinking!

False

False

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False

### If you stood on a planet having a mass four times higher than Earth's mass, and a radius two times longer than Earth's radius, you would weigh a. the same as you do on Earth b. two times more than you do on Earth. c. two times less than you do on Earth d. four times more than you do on Earth. e. four times and as half more than you do on Earth. f. six times more than you do on Earth.

the same as you do on Earth

### A donkey pulls a crate up a rough, inclined plane at constant speed. Which one of the following statements concerning this situation is FALSE? a. The gravitational potential energy of the crate is increasing. b. The net work done by all the forces acting on the crate is zero joules. c. The work done on the crate by the normal force of the plane is zero joules. d. The donkey does "positive" work in pulling the crate up the incline. e. The work done on the object by gravity is zero joules.

The work done on the object by gravity is zero joules.

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