Fisicks 2325 Midterm

In the figure, four point masses are placed as shown. The x and y coordinates of the center of mass are closest to

(2.3 m, 2.8 m).

A uniform solid sphere has a moment of inertia I about an axis tangent to its surface. What is the moment of inertia of this sphere about an axis through its center?

(2/7)*I

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine the x and y components of Vector B.

-25, 0 cm

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine the x and y components of Vector C.

-28, -28 cm

Write out the number 7.35 × 10^−5 in full with a decimal point and correct number of zeros.

0.0000735

A boy throws a rock with an initial velocity of 2.15 m/s at 30.0° above the horizontal. If air resistance is negligible, how long does it take for the rock to reach the maximum height of its trajectory?

0.110 s

A 5.00-kg box slides 4.00 m across the floor before coming to rest. What is the coefficient of kinetic friction between the floor and the box if the box had an initial speed of 3.00 m/s?

0.115

The following exact conversion equivalents are given: 1 m = 100 cm, 1 in = 2.54 cm, and1 ft = 12 in. If a computer screen has an area of 1.27 ft2, this area is closest to

0.118 m^2

A 1.2-kg spring-activated toy bomb slides on a smooth surface along the x-axis with a speed of 0.50 m/s. At the origin 0, the bomb explodes into two fragments. Fragment 1 has a mass of 0.40 kg and a speed of 0.90 m/s along the negative y-axis. In the figure, the energy released by the explosion is closest to

0.32 J

A very light 1.00-m wire consists of two segments of equal length, one of steel (Young's modulus is 2.00 × 10^11 N/m^2) and one of brass (Young's modulus is 9.0 × 10^10 N/m2). The steel segment is 1.50 mm in diameter, and the brass segment has twice this diameter. When a weight w is hung from the ceiling by this wire, the steel segment stretches by 1.10 mm. By what distance does the brass segment stretch?

0.61 mm

As part of an exercise program, a woman walks south at a speed of 2.00 m/s for 60.0 minutes. She then turns around and walks north a distance 3000 m in 25.0 minutes. What is the woman's average velocity during her entire motion?

0.824 m/s south

How much energy is needed to change the speed of a 1600 kg sport utility vehicle from 15.0 m/s to 40.0 m/s?

1.10 MJ

A student slides her 80.0-kg desk across the level floor of her dormitory room a distance 4.00 m at constant speed. If the coefficient of kinetic friction between the desk and the floor is 0.400, how much work did she do?

1.26 kJ

A soccer ball is released from rest at the top of a grassy incline. After 8.6 seconds, the ball travels 87 meters and 1.0 s after this, the ball reaches the bottom of the incline. How long was the incline?

110 m

Determine the scalar product of A = 6.0i + 4.0j - 2.0k and B = 5.0i - 6.0j - 3.0k.

12

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine x and y components of the sum of these three vectors.

12, 9.2 cm

A very thin uniform rod, 2.40 m long and of weight 135 N, has a frictionless hinge at its lower end. It starts out vertically from rest and falls, pivoting about the hinge. Just as it has rotated through an angle of 55.0°, what is the downward acceleration of the end farthest from the hinge?

12.0 m/s^2

The position of an object is given by x = at^3 - bt^2 + ct, where a = 4.1 m/s^3, b = 2.2 m/s^2, c = 1.7 m/s, and x and t are in SI units. What is the instantaneous acceleration of the object when t = 0.7 s?

13 m/s^2

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine the magnitude of the sum of these three vectors.

15 cm

Vectors A and B are shown in the figure. Vector C is given by C = B − A. The magnitude of vector A is 16.0 units, and the magnitude of vector B is 7.00 units. What is the magnitude of vector C?

16.2

A spring stretches by 21.0 cm when a 135 N object is attached. What is the weight of a fish that would stretch the spring by 31.0 cm?

199 N

As part of an exercise program, a woman walks south at a speed of 2.00 m/s for 60.0 minutes. She then turns around and walks north a distance 3000 m in 25.0 minutes. What is the woman's average speed during her entire motion?

2.00 m/s south

A soccer ball is released from rest at the top of a grassy incline. After 8.6 seconds, the ball travels 87 meters and 1.0 s after this, the ball reaches the bottom of the incline. What was the magnitude of the ball's acceleration, assume it to be constant?

2.4 m/s^2

The following four forces act on a 4.00 kg object: F1 = 300 N east; F2 = 700 N north; F3 = 500 N west; F4 = 600 N south; What is the acceleration of the object?

224 N in a direction 26.6° north of west

The figure shows two wires tied to a 3.3 kg sphere that revolves in a horizontal circle at constant speed. At this particular speed the tension is the same in both wires. What is the tension?

24 N

If B = -2i - 6j + 2k and vector C = -2i -2j - 3k, which of the following numbers is closest to the magnitude of C × B?

25

A small boat is moving at a velocity of 3.35 m/s when it is accelerated by a river current perpendicular to the initial direction of motion. If the acceleration of the current is 0.750 m/s2, what will be the new velocity of the boat after 33.5 s?

25.3 m/s at 82.4° from initial direction of motion

A rock is thrown directly upward from the edge of the roof of a building that is 66.2 meters tall. The rock misses the building on its way down, and is observed to strike the ground 4.00 seconds after being thrown. Neglect any effects of air resistance. With what speed was the rock thrown?

3.05 m/s

A stationary 1.67-kg object is struck by a stick. The object experiences a horizontal force given by F = at - bt^2, where t is the time in milliseconds from the instant the stick first contacts the object. If a = 1500 N/(ms) and b = 20 N/(ms)^2, what is the speed of the object just after it comes away from the stick at t = 2.74 ms?

3.3 m/s

The base of an aluminum block, which is fixed in place, measures 90 cm by 90 cm, and the height of the block is 60 cm. A force, applied to the upper face and parallel to it, produces a shear strain of 0.0060. The shear modulus of aluminum is 3.0 × 1010 N/m2. What is the displacement of the upper face in the direction of the applied force?

3.6 mm

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine the direction of the sum of these three vectors.

38° above the x-axis

A ball rolls across a floor with an acceleration of 0.100 m/s^2 in a direction opposite to its velocity. The ball has a velocity of 4.00 m/s after rolling a distance 6.00 m across the floor. What was the initial speed of the ball?

4.15 m/s

Express (4.3 × 10^6)^−1/2 in scientific notation.

4.8 × 10^−4

A 1.20-kg ball is hanging from the end of a rope. The rope hangs at an angle 25.0° from the vertical when a 15.0 m/s horizontal wind is blowing. If the wind's force on the rope is negligible, what drag force does the wind exert on the ball?

5.48 N

A solid, uniform sphere of mass 2.0 kg and radius 1.7 m rolls from rest without slipping down an inclined plane of height 7.0 m. What is the angular velocity of the sphere at the bottom of the inclined plane?

5.8 rad/s

The acceleration of an object as a function of time is given by a(t) = (3.00 m/s^3)t, where t is in seconds. If the object is at rest at time t = 0.00 s, what is the velocity of the object at time t = 6.00 s?

54.0 m/s

Vector A has a magnitude of 75.0 cm and points at 30° above the positive x-axis. Vector B has a magnitude of 25.0 cm and points along the negative x-axis. Vector C has a magnitude of 40.0 cm and points at 45° below the negative x-axis Determine the x and y components of Vector A.

65, 38 cm

The magnitude of the drag force of air resistance on a certain 20.0-kg object is proportional to its speed. If the object has a terminal speed 80.0 m/s, what is the magnitude of the drag force on the object when it is falling with a speed 30.0 m/s?

73.5 N

A block is on a frictionless horizontal table, on earth. This block accelerates at 1.9 m/s2 when a 90 N horizontal force is applied to it. The block and table are then set up on the moon where the acceleration due to gravity is 1.62 m/s^2. What is the weight of the block on the moon?

77 N

An airplane undergoes the following displacements: First, it flies 66 km in a direction 30° east of north. Next, it flies 49 km due south. Finally, it flies 100 km 30° north of west. Using vector components, determine how far the airplane ends up from its starting point.

79 km

You are standing on a skateboard, initially at rest. A friend throws a very heavy ball towards you. You can either catch the object or deflect the object back towards your friend (such that it moves away from you with the same speed as it was originally thrown). What should you do in order to MINIMIZE your speed on the skateboard?

Catch the ball

If an object is accelerating toward a point, then it must be getting closer and closer to that point.

False

If two nonzero vectors point in the same direction, their dot product must be zero.

False

When determining the number of significant figures in a number, zeroes to the left of the decimal point are never counted.

False

If a tree is 15 m tall, its height expressed in feet is x ft, where x is

Greater than 15

You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. The force acting on you that causes you to fall forward is

No forces were acting on you to cause you to fall.

The plot in the figure shows the potential energy of a particle, due to the force exerted on it by another particle, as a function of distance. At which of the three points labeled in the figure is the magnitude of the force on the particle greatest?

Point X

For the vectors shown in the figure, express vector S in terms of vectors M and N

S =M−N

A small car has a head-on collision with a large truck. Which of the following statements concerning the magnitude of the average force due to the collision is correct?

The small car and the truck experience the same average force.

Jan and Len throw identical rocks off a tall building at the same time. The ground near the building is flat. Jan throws her rock straight downward. Len throws his rock downward and outward such that the angle between the initial velocity of the rock and the horizon is 30°. Len throws the rock with a speed twice that of Jan's rock. If air resistance is negligible, which rock hits the ground first?

They hit at the same time.

A 1.15-kg grinding wheel 22.0 cm in diameter is spinning counterclockwise at a rate of 20.0 revolutions per second. When the power to the grinder is turned off, the grinding wheel slows with constant angular acceleration and takes 80.0 s to come to a rest. a) What was the angular acceleration (in rad/s2) of the grinding wheel as it came to rest if we take a counterclockwise rotation as positive? b) How many revolutions did the wheel make during the time it was coming to rest?

a) -1.57 rad/s^2 b) 800 revolutions

The horizontal coordinates of a Frisbee in a strong wind are given by x = -12t + 4t ^2 and y = 10t - 3t ^2, where x and y are in meters, and t is in seconds. a) What is the magnitude of the acceleration of the Frisbee? b) What is the direction of the acceleration of the Frisbee? c) What is the magnitude of the velocity at t = 2.0 s?

a) 10.0 m/s^2 b) 37 degrees c) 4.5 m/s

A wind farm generator uses a two-bladed propeller (see figure) mounted on a pylon at a height of 20 m. The length of each propeller blade is 12 m. A small piece from the tip of the propeller breaks off when the propeller is vertical. At that instant, the period of the motion of the propeller is 1.2 s. The fragment flies off horizontally, falls with negligible air resistance, and strikes the ground at P. a) How far is point P from the base of the pylon? b) At what angle with respect to the vertical is the fragment moving just as it strikes the ground at P?

a) 160 m b) 68°

An airplane is flying at a speed of 2.00 × 102 m/s in level flight at an altitude of 8.00 × 102 m. A package is to be dropped from the airplane to land on a target on the ground. Ignore air resistance. a) At what horizontal distance away from the target should the package be released so that it lands on the target? b) In what direction relative to the horizontal will the package be traveling when it hits the ground?

a) 2.56 km b) 32.1° below the horizontal

A 3.00-kg ball rests in a frictionless groove as shown in the figure. a) What is the magnitude of the force that the left side of the groove exerts on the ball? b) What is the magnitude of the force that the right side of the groove exerts on the ball?

a) 26.4 N b) 21.5 N

Two objects are connected by a very light flexible string as shown in the figure, where M = 0.60 kg and m = 0.40 kg. You can ignore friction and the mass of the pulley. a) Draw free-body diagrams for each object. b) Calculate the magnitude of the acceleration of each object.

a) pictured b) 2.0 m/s^2 c) 4.7 N

The motion of a particle is described in the velocity versus time graph shown in the figure. We can say that its speed

decreases and then increases.

As you are leaving a building, the door opens outward. If the hinges on the door are on your right, what is the direction of the angular velocity of the door as you open it?

down

In order to get an object moving, you must push harder on it than it pushes back on you.

false

The position x, in meters, of an object is given by the equation x = A + Bt + Ct ^2, where t represents time in seconds. What are the SI units of A, B, and C?

m, m/s, m/s^2

In the figure, determine the character of the collision. The masses of the blocks, and the velocities before and after are given. The collision is

perfectly elastic

A uniform disk, a uniform hoop, and a uniform solid sphere are released at the same time at the top of an inclined ramp. They all roll without slipping. In what order do they reach the bottom of the ramp?

sphere, disk, hoop

While an object is in projectile motion (with upward being positive) with no air resistance

the horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to -g.

Tensile strain is

the ratio of the change in length to the original length

A 3.00-kg ball swings rapidly in a complete vertical circle of radius 2.00 m by a light string that is fixed at one end. The ball moves so fast that the string is always taut and perpendicular to the velocity of the ball. As the ball swings from its lowest point to its highest point

the work done on it by gravity is -118 J and the work done on it by the tension in the string is zero.

A packing crate rests on a horizontal surface. It is acted on by three horizontal forces: 600 N to the left, 200 N to the right, and friction. The weight of the crate is 400 N. If the 600-N force is removed, the resultant force acting on the crate is

zero

If A and B are nonzero vectors for which A*B=0, it must follow that

|A × B| = AB.