PHYS 111 Midterm

What is the cost to run a 900 W medium-sized window air conditioning unit for 8.0 hours if the electricity company charges $0.20 per kW-hr?

$1.44

A student moves 3.0 m south, 6.0 m east, and 1.0 m north. What is the angle of the displacement?

-18 degrees

Examine the position vs. time graph below. What is the velocity of the object at t = 5.0 s?

-5 m/s

Convert 4200 cm to miles. (1 mi = 1.6 km)

0.026 mi

A student kicks a ball so that the ball's initial velocity is 8.3 m/s at 30°. How much time does the ball spend in the air?

0.9 s

A student throws a rock horizontally off a 5.0 m tall building. The rock's initial speed is 6.0 m/s. How long will it take the rock to reach the ground? Air resistance is negligible.

1.0 s

A student gives a 5.0 kg box a brief push causing the box to move with an initial speed of 8.0 m/s along a rough surface. The box experiences a friction force of 30 N as it slows to a stop. How long does it take the box to stop?

1.3 s

A student pushes a 0.2 kg box against a spring causing the spring to compress 0.15 m. When the spring is released, it will launch the box vertically into the air. What is the maximum height the box will reach if the spring constant is 300 N/m?

1.7 m

What is the gravitational potential energy of a 4.0 kg cat that is stuck in a tree 3.0 m from the ground?

118 J

A student standing on the edge of a cliff throws a rock downward at a speed of 7.5 m/s at an angle 40° below the horizontal. It takes the rock 2.4 seconds to hit the ground. How far from the base of the cliff will the rock land?

13.8 m

Convert 35.0 mph to m/s. (1 mi = 1.6 km)

15.6 m/s

A jogger starts at a position of 4.0 m and moves forwards at a constant rate ending at a position of 12.0 m at a time 4.0 s later. What is the speed of the jogger?

2.0 m/s

How long will it take an object to travel a distance of 50 m if it starts from rest and accelerates at a rate of 12 m/s2?

2.9s

What is the kinetic energy of a 1000 kg car traveling at a speed of 20 m/s?

200 kJ

A person driving through a field has velocity components that are 30 m/s west and 20 m/s south. What is the approximate direction of the overall velocity?

214 degrees

A car accelerates from rest at a rate of 20 m/s2. How far will the car have traveled by the time it reaches a speed of 30 m/s?

22.5m

A student stretches an elastic band by 0.8 m in 0.5 seconds. The spring constant of the elastic band is 40 N/m. What was the power exerted by the student?

25.6 W

A student applies a steadily increasing horizontal force to a 40 kg box over a distance of 10 m. The graph of the student's force vs. distance traveled is shown below. How much work did the student do on the box?

250 J

What angle is necessary to keep a 10 kg box motionless if the coefficient of static friction between the box and the ramp is 0.55?

28.8 degrees

A student runs off of a diving platform with a speed of 2.5 m/s and hits the water 0.8 seconds later. What is the height of the platform?

3.1 m

A student applies a constant horizontal 20 N force to a 12 kg box that is initially at rest. The student moves the box a distance of 3.0 m. What is the speed of the box at the end of the motion? Assume negligible friction.

3.2 m/s

A student drops a 1.5 kg rock off of a 4.0 m tall bridge. The speed of the rock just before it hits the water below is 6 m/s. How much energy was lost due to air resistance?

31.8 J was lost

A person driving through a field has velocity components that are 30 m/s west and 20 m/s south. What is the magnitude of the overall velocity?

36 m/s

A student rolls two balls off of a table. Ball A has twice the mass of ball B. Both balls leave the table at the same time with the same starting velocity. Which ball will hit the ground first? (Air resistance is negligible.)

4.5 m

A student pushes a 0.5 kg box against a spring causing the spring to compress 0.15 m. What is the final speed of the box when the student releases the spring? The spring constant is 450 N/m. Friction is negligible.

4.5 m/s

A student kicks a ball off the ground such that the ball has an initial speed of 17 m/s at some angle. Which of the following starting velocity angles will result in the greatest horizontal distance?

40 degrees

What is the horsepower required for a 1200 kg car to travel from rest to a speed of 20 m/s in 7.0 seconds? (746 W = 1 hp)

46 hp

Examine the velocity vs. time graph below. What is the total displacement?

4m

Vector A has components A = <-2, 5> m/s and vector B has components B = <6, -2> m/s. What is the magnitude of vector C if C = A + B?

5 m/s

A student kicks a ball so that the ball's initial velocity is 12 m/s at 60°. What is the maximum height of the ball?

5.5 m

The grid below shows two vectors <strong>A</strong> and <strong>B</strong>. What is the magnitude of the sum of the vectors <srong>A</strong>+<strong>B</strong>?

5.7 m

Suppose that an airplane flying 70 m/s at a height of 300 m drops a crate. What horizontal distance will the crate have traveled when it hits the ground? Assume negligible air resistance.

548 m

A student moves 8.0 m to the west, 6.0 m to the north, and 10.0 m to the east. What is the magnitude of the displacement?

6.3m

A medium-sized air conditioning unit is rated at 900 W. How much energy will the AC unit require in order to operate for 2.0 hours?

6.48x106 J

A student applies a horizontal force of 100 N to a 25 kg box causing the block to accelerate at a rate of 1.5 m/s/s. Which of the following is the best approximation of the magnitude of the friction force on the box?

63N

A student moves forwards 10 m and backwards 4 m. What is the magnitude of the displacement of the student?

6m

How much time will it take for a car traveling at a velocity of -4.0 m/s to travel a distance of 30 m?

7.5s

A 500 kg rollercoaster car starts from rest at the top of a 10.0 m tall hill. It then travels down the track and up a loop. The top of the loop is 7.0 m from the ground. What is the speed of the rollercoaster car at the top of the loop assuming negligible friction losses?

7.7 m/s

A car moving at a constant 25 m/s travels for 3.0 seconds. What is the distance traveled by the car?

75m

An airplane in the process of taking off travels with a speed of 80 m/s at an angle of 15° above the horizontal. What is the ground speed of the airplane?

77 m/s

The grid below shows the path a student takes through a campus area. What is the approximate magnitude of the student's overall displacement? (Be careful—this is not a position vs. time graph.)

7m

Examine the velocity vs. time graph below. What is the total distance?

8m

A student rolls two balls off of a table. Ball A has twice the mass of ball B. Both balls leave the table with the same starting velocity. Which ball will land further away from the table? (Air resistance is negligible.)

A and B will land the same distance from the table

A student rolls two balls off of a table. Ball A has twice the mass of ball B. Both balls leave the table at the same time with the same starting velocity. Which ball will hit the ground first? (Air resistance is negligible.)

A will hit the ground at the same time as B

A student rolls two identical balls off of a table. Both balls leave the table at the same time, but ball B has twice the starting velocity. Which ball will hit the ground first? (Air resistance is negligible.)

A will hit the ground at the same time as B

Which of the following is an example of a vector measurement?

Acceleration

A plane flying overhead releases a package. A stationary observer watches the path of the package as it falls. Which of the following paths will the observer see assuming negligible air resistance?

D

Mass M is at rest on a frictionless table and is attached by a light string across a frictionless, massless pulley to mass m which is suspended as shown below: The masses are released from rest. Which of the following correctly describes the energy changes for each of the masses?

D) K increases while Ug remains constant. K increases while Ug decreases.

A student wants to compare a set of measurements in order to analyze the precision of an instrument. Which of the following methods would be most appropriate?

Examine the percent difference between the largest and smallest measured values

Examine the position vs. time graph below. Which of the following correctly describes the motion of the object?

Forwards at a constant speed and then backwards at a constant speed

Which of the following statements concerning speed and velocity is most accurate?

Speed does not depend on direction but velocity does.

The applied force vs. distance stretched data for two different springs A and B is shown on the graph below. Which spring has the largest spring constant?

Spring A has the largest spring constant.

Three students move identical tables across identical carpeted floors with the same applied force. The direction of the applied force on table A is horizontal. The direction of the applied force on table B is 45° below the horizontal. The direction of the applied force on table C is 45° above the horizontal (see below). Which table will experience the smallest friction force?

Table C will experience the smallest friction force

A student fires a bullet horizontally from a gun. Which statement is most accurate?

The bullet will start to fall as soon as it leave the gun.

A student measures the mass of an object at 4.68 g. Which of the following statements is most accurate?

The first two digits are measured and the last digit is estimated.

A student jumps out of a plane and activates her parachute a few seconds later. How does the force of the parachute on the student compare to the force of the student on the parachute?

The force of the parachute on the student is equal to the force of the student on the parachute.

A student measures the mass of an object at 4.68 g and the volume of the object at 2.3 mL. The student calculates the density as 2.03478 g/mL. A second student disagrees with the density. Which of the following statements would explain why the second student disagrees?

The number of decimals in the answer does not show proper precision.

A student models the constant speed motion of an object with the following equation: x = (4 m/s) t + (-15 m) Which of the following descriptions of motion is consistent with this equation?

The object starts at a negative position and travels forwards.

A student models the constant speed motion of an object with the following equation: x = (-2 m/s) t + (4 m) Which of the following descriptions of motion is consistent with this equation?

The object starts at a positive position and travels backwards.

Which of the following is NOT considered a mechanical form of energy?

Work

A block slides down an inclined plane. The block experiences some amount of friction. Which of the following changes would result in a decrease in friction?

an increase in the angle of the ramp

Which of the following is a vector measurement?

displacement

A student throws a ball. Which of the following force vector diagrams shows all of the forces acting on the ball when the ball has reached its maximum height? Air resistance is negligible.

down

A horse applies a 200 N force to a sled causing the sled to accelerate. What will the force of the sled be on the horse?

equal to 200 N

Mars has a gravitational field strength of 3.7 N/kg near its surface. If air resistance is negligible, then an object dropped on Mars would have an acceleration that is

equal to 3.7 m/s2.

A student plans to experimentally determine the coefficient of static friction between a box and the ground. The student places the box on the ground and uses a force sensor to measure the force required to start moving the box. What additional information will the student need?

more than one of the above

A negative acceleration indicates that an object might be

moving forward while slowing down

The coefficient of friction is commonly reported using which of the following units?

none of the above

The following force vector diagram shows all of the forces acting on a box. Which of the following correctly describes the motion of the box?

none of the above describe the motion of the box

Energy is best defined as

the ability to make a system change in some way

A student drops a ball off the top of a tall building. The ball accelerates downward with air resistance. Consider the ball some time before it has reached terminal velocity. Which of the following is the reaction pair force (i.e., Newton's third law pair) to the force of gravity on the ball?

the force of the ball pulling up on the earth

A student throws a rock through a glass window causing the window to shatter. How does the force of the rock on the window compare to the force of the window on the rock?

the force of the rock on the window is equal to the force of the window on the rock

A student applies a steady 100 N force at an angle 45° below the horizontal to a 25 kg box. The maximum static friction force on the box is 100 N. Which of the following is the Newton's third law reaction pair force to the 100 N force applied by the student?

the net force on sphere A is qual to the net force on sphere B

Sphere A is initially at rest on the ground and is kicked so that it has an initial velocity of vo at an angle of θ. Sphere B is also initially at rest on the ground and kicked so that it has an initial velocity is 2vo at the same angle θ. Air resistance is negligible. The two spheres are identical. Consider both spheres at the moment when they have reached their respective maximum heights. Which of the following statements is accurate?

the question does not provide enough information to tell which net force is larger

Power is best defined as

the rate of energy transfer

A system experiences an amount of work with a negative value. Which statement correctly interprets the significance of the negative sign?

the system lost energy

A student throws a ball straight up into the air. When the ball reach its maximum height,

the velocity of the ball is zero, and the acceleration is negative.

An elevator moves upwards while getting faster. Which of the following statements is correct?

work is converted into kinetic and gravitational energy

A car starts at a position of 25 m and travels backwards at a constant speed of 5 m/s. Which of the following equations correctly models this movement?

x = (-5 m/s)(t) + (25 m)

Work is done on a spring causing the spring to compress an amount x. If the total work done on the spring is doubled, what will the total spring compression be?

x√2