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RIO SOLADO - PHY 111 Midterm 1
QUESTIONS AND ANSWERS
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? - CORRECT ANSWER -6.3 m Examine the position vs. time graph below. What is the velocity of the object at t = 5.0 s? - CORRECT ANSWER --5 m/s 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? - CORRECT ANSWER -The number of decimals in the answer does not show proper precision. Examine the position vs. time graph below. Which of the following correctly describes the motion of the object? - CORRECT ANSWER -Forwards at a constant speed and then backward at a constant speed A car moving at a constant 25 m/s travels for 3.0 seconds. What is the distance traveled by the car? - CORRECT ANSWER -75 m
A student measures the mass of an object at 4.68 g. Which of the following statements is most accurate? - CORRECT ANSWER -he first two digits are measured and the last digit is estimated. 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? - CORRECT ANSWER -The object starts at a negative position and travels forwards. How much time will it take for an object traveling at a constant speed of 20 m/s to travel 15 m? - CORRECT ANSWER -0.75 s 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? - CORRECT ANSWER -The object starts at a positive position and travels backwards.
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? - CORRECT ANSWER -7.5 m 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? - CORRECT ANSWER -2.0 m/s A student moves 3.0 m south, 6.0 m east, and 1.0 m north. What is the angle of the displacement? - CORRECT ANSWER --18° The grid below shows two vectors A and B. What is the magnitude of the sum of the vectors A+B? - CORRECT ANSWER -5. A student launches a rocket with some initial velocity v at some angle θ. The rocket hits a wall on its way back down to the ground. (See the diagram below.) Which of the following statements is most accurate? - CORRECT ANSWER -The speed of the rocket just before it hits the wall is less than the starting speed of the rocket. 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. - CORRECT ANSWER -548 m
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? - CORRECT ANSWER -13.8 m 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? - CORRECT ANSWER -5.5 m A student runs off of a diving platform with a speed of 2.5 m/s and hits the water 1.8 seconds later. What is the student's horizontal distance from the platform when she hits the water? Air resistance is negligible. - CORRECT ANSWER -4.5 m 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? - CORRECT ANSWER -3.1 m 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? - CORRECT ANSWER -0.9 s Which of the following is the closest approximation of the vertical component of a velocity that is 40 m/s at 80°? - CORRECT ANSWER -39 m/s A student launches a small 0.5 kg rocket with an initial speed of 30 m/s at an angle of 60°. Approximately how much time will the rocket spend in the air? Air resistance is negligible. - CORRECT ANSWER -5.3 s
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? - CORRECT ANSWER -5 m/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. - CORRECT ANSWER -1.0 s A student fires a bullet horizontally out of a gun. At the same time the bullet leaves the gun, the student drops a second bullet from the same height. Which bullet hits the ground first? - CORRECT ANSWER -The two bullets will hit the ground at the same time. 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.) - CORRECT ANSWER -A and B will land the same distance from the table. 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 - CORRECT ANSWER -equal to 3.7 m/s2. 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? - CORRECT ANSWER -2.9 s 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? - CORRECT ANSWER -22.5 m
A box moving on a horizontal surface with an initial velocity of 20 m/s slows to a stop over a time period of 5.0 seconds due solely to the effects of friction. What is the coefficient of kinetic friction between the box and the ground? - CORRECT ANSWER -0. 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? - CORRECT ANSWER -Table C will experience the smallest friction force. A negative acceleration indicates that an object might be - CORRECT ANSWER - moving forward while slowing down. An 800 kg car starts from rest and travels a distance of 75.0 m in 5.0 seconds. Which of the following is the correct net force acting on the car during this time? - CORRECT ANSWER -4800 N 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? - CORRECT ANSWER -The net force on sphere A is equal to the net force on sphere B.
A student throws a ball straight up into the air. When the ball reach its maximum height, - CORRECT ANSWER -the velocity of the ball is zero, and the acceleration is negative. A student applies a 147 N force at an angle 30° below the horizontal to a 15.0 kg box at rest on the ground. The coefficient of static friction is 0.7, and the coefficient of kinetic friction is 0.5. Describe the motion of the box. - CORRECT ANSWER -The box will remain motionless. 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. - CORRECT ANSWER - 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? - CORRECT ANSWER -The force of the parachute on the student is equal to the force of the student on the parachute. 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? - CORRECT ANSWER -63 N A large truck moving at 30 mph collides with a parked car. How does the force of the truck on the car compare to the force of the car on the truck? - CORRECT ANSWER -The force of the truck on the car is equal to the force of the car on the truck.
A system experiences an amount of work with a negative value. Which statement correctly interprets the significance of the negative sign? - CORRECT ANSWER -The system lost energy. 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? - CORRECT ANSWER -6.48x106 J 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? - CORRECT ANSWER -Spring A has the largest spring constant. Which of the following is NOT considered a mechanical form of energy? - CORRECT ANSWER -Work A student connects a 300 kg container to a rope and pulley system and then connects the rope to a motor. If the student wants to lift the container 10.0 m in 2.0 min, what average power rating is required? - CORRECT ANSWER -245 W A student sets a box at the top of a ramp with a steep angle of incline. The box will start from rest and will slide down the ramp and up a second ramp whose angle of incline is much less steep. Point P shows the position on the second ramp that is at the same height as the block's starting point in the first ramp. Which of the following statements is correct? Assume negligible friction losses. - CORRECT ANSWER -The box will just barely hit point P before it starts to slide back down the second ramp.
An elevator moves upwards while getting faster. Which of the following statements is correct? - CORRECT ANSWER -Work is converted into kinetic and gravitational energy. How much energy is stored in spring that has been compressed 0.20 m if the spring constant is 300 N/m? - CORRECT ANSWER -6 J 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?
- CORRECT ANSWER -1.7 m Power is best defined as - CORRECT ANSWER -rate of energy transfer A car travels at a constant speed up a hill from point A to point B as shown in the diagram below. Which of the following statements is most correct? - CORRECT ANSWER -The gravitational energy increases, and the kinetic energy remains the same. A student connects a 1 hp motor to a bicycle. How much time will it take for the bicycle to accelerate from rest to a speed of 5.0 m/s if the combined mass of the student and the bicycle is 120 kg? (1 hp = 746 W) - CORRECT ANSWER -2 sec 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) - CORRECT ANSWER -46 hp
Energy is best defined as - CORRECT ANSWER -the ability to make a system change in some way.
