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What we found:

Three students are pulling on a bag of skittles. Each is pulling with a horizontal force. If student 1 pulls Eastward with 170 N, student 2 pulls Southward with 100 N and student 3 pulls with 200 N at an angle of 20° west of north, what is the net force caused by the three students on the bag of skittles?

A person pulls a rope with a force \( F \) at an angle of \( 60^\circ \) to the horizontal. The rope is connected to a load over a frictionless pulley as shown in the diagram. The load is stationary. Which of the following is correct about the weight of the load and the net force exerted on the pulley by the rope?

A \( 4700 \, \text{kg} \) truck carrying a \( 900 \, \text{kg} \) crate is traveling at \( 25 \, \text{m/s} \) to the right along a straight, level highway, as shown above. The truck driver then applies the brakes, and as it slows down, the truck travels \( 55 \, \text{m} \) in the next \( 3.0 \, \text{s} \). The crate does not slide on the back of the truck.

A small block slides without friction along a track toward a circular loop. The block has more than enough speed to remain firmly in contact with the track as it goes around the loop. The magnitude of the block’s acceleration at the top of the loop is

A person stands on a scale in an elevator. If the scale reads \( 600 \, \text{N} \) when that person is riding upward at a constant velocity of \( 4 \, \text{m/s} \), what is the scale reading when the elevator is at rest?

A ball of mass \( m \) is suspended from two strings of unequal length as shown above. The magnitudes of the tensions \( T_1 \) and \( T_2 \) in the strings must satisfy which of the following relations?

A rope of negligible mass supports a block that weighs 30 N, as shown above. The breaking strength of the rope is 50 N. The largest acceleration that can be given to the block by pulling up on it with the rope without breaking the rope is most nearly

The cart with mass \( M = 3 \, \text{kg} \) is pulled by a massless string and moving on a horizontal track. A weight with mass \( m = 1 \, \text{kg} \) is hung from the other end of the string through a pulley system. Due to the gravitational force acting on the weight of mass \( m \), the cart is accelerated to the left. Find the tension in the string.

A “doomsday” asteroid with a mass of 1010 kg is hurtling through space. Unless the asteroid’s speed is changed by about 0.20 cm/s, it will collide with Earth and cause tremendous damage. Researchers suggest that a small “space tug” sent to the asteroid’s surface could exert a gentle constant force of 2.5 N. For how long must this force act?

A crane’s trolley at point \( P \) moves for a few seconds to the right with constant acceleration, and the \( 870 \, \text{kg} \) load hangs on a light cable at a \( 5^\circ \) angle to the vertical as shown. What is the acceleration of the trolley and load?

A child slides down a slide with a \( 34^\circ \) incline, and at the bottom her speed is precisely half what it would have been if the slide had been frictionless. Calculate the coefficient of kinetic friction between the slide and the child.

A pair of fuzzy dice is hanging by a string from your rearview mirror. You speed up from a stoplight. During the acceleration, the dice do not move vertically; the string makes an angle of \( 22^\circ \) with the vertical. The dice have a mass of \( 0.10 \, \text{kg} \). Determine the acceleration.

A \( 0.20 \) \( \text{kg} \) object moves along a straight line. The net force acting on the object varies with the object’s displacement as shown in the graph above. The object starts from rest at displacement \( x = 0 \) and time \( t = 0 \) and is displaced a distance of \( 20 \) \( \text{m} \). Determine each of the following.

Four blocks of masses \( 20 \, \text{kg}, \, 30 \, \text{kg}, \, 40 \, \text{kg}, \, \text{and} \, 50 \, \text{kg} \) are stacked on top of one another in an elevator in order of decreasing mass with the lightest mass on the top of the stack. The elevator moves downward with an acceleration of \( 3.2 \, \text{m/s}^2 \). Find the contact force between the \( 30 \, \text{kg} \) and \( 40 \, \text{kg} \) masses.

Two masses, \(m1\) and \(m2\), are connected by a cord and arranged as shown in the diagram with m1 sliding along on a frictionless surface and \(m2\) hanging from a light frictionless pulley. What would be the mass of the falling mass,\(m2\), if both the sliding mass,\(m1\), and the tension, \(T\), in the cord were known?

An \( 80 \, \text{kg} \) block is placed \( 2 \, \text{m} \) away from the endpoint of a horizontal steel beam of length \( 6.6 \, \text{m} \) and mass \( 1,450 \, \text{kg} \). The plank makes contact with a vertical wall on one end, and the other endpoint is attached to a massless cable that makes an angle of \( 30^\circ \) with the horizontal and ties into the vertical wall as well. Calculate the magnitude and direction of the force between the cable and the wall and of the force between the steel beam and the wall.

A block of weight \( W \) is pulled along a horizontal surface at constant speed by a force \( F \), which acts at an angle of \( \theta \) with the horizontal. The normal force exerted on the block by the surface has magnitude:

Which of the following must be true for an object at translational equilibrium?

A coffee cup on the dashboard of a car slides forward when the driver decelerates from \( \frac{45 \, \text{km}}{\text{h}} \) to rest in \( 3.5 \) seconds or less. What is the coefficient of static friction between the cup and the dash? Assume the road and the dashboard are level (horizontal).

A car can decelerate at \( -3.80 \, \text{m/s}^2 \) without skidding when coming to rest on a level road. What would its deceleration be if the road is inclined at \( 9.3^\circ \) and the car moves uphill? Assume the same static friction coefficient.

A child on a sled reaches the bottom of a hill with a velocity of \( 10.0 \, \text{m/s} \) and travels \( 25.0 \, \text{m} \) along a horizontal straightaway to a stop. If the child and sled together have a mass of \( 60.0 \, \text{kg} \), what is the average retarding force on the sled on the horizontal straightaway?

A skateboarder, with an initial speed of \( 20.0 \, \text{m/s} \), rolls virtually friction-free down a straight incline of length \( 18 \, \text{m} \) in \( 3.3 \, \text{s} \). At what angle is the incline oriented above the horizontal?

A horizontal, uniform board of weight \( 125 \, \text{N} \) and length \( 4 \, \text{m} \) is supported by vertical chains at each end. A person weighing \( 500 \, \text{N} \) is hanging from the board. The tension in the right chain is \( 250 \, \text{N} \).

A block of mass \( m \), acted on by a force \( F \) directed horizontally, slides up an inclined plane that makes an angle \( \theta \) with the horizontal. The coefficient of sliding friction between the block and the plane is \( \mu \).

An adult exerts a horizontal force on a swing that is suspended by a rope of length \( L \), holding it at an angle \( \theta \) with the vertical. The child in the swing has a weight \( W \) and dimensions that are negligible. In terms of \( W \) and \( \theta \), determine:

A uniform rope of weight \( 30 \, \text{N} \) hangs from a hook. A box of mass \( 40 \, \text{kg} \) is suspended from the rope. What is the tension in the rope?

A box with a mass of M rests on a balance in an elevator that is moving downwards. The elevator slows with an acceleration of g/4. Which of the following gives the reading of the balance?

A box is sliding down an incline at a constant speed of 2 m/s2. The angle of the incline is θ. The magnitude of the total of the opposing forces is 16 N. What is the force of gravity acting on the box?

An airplane of weight \( W \) is flying horizontally with constant velocity. The total forward thrust of the engines is \( 3W \). What is the magnitude of the force of the air on the plane in terms of \( W \)

The elliptical orbit of a comet is shown above. Positions 1 and 2 are, respectively, the farthest and nearest positions to the Sun, and at position 1 the distance from the comet to the Sun is 10 times that at position 2. What is the ratio \( F_1 / F_2 \), the force on the comet at position 1 to the force on the comet at position 2?

An object is moving at constant velocity. Which of the following could be the free-body diagram representing the forces acting on the object?

A piece of metal of weight\(W\) is suspended by two identical strings. Each string passes through a pulley and is attached to a block of mass \(m\) . The system is in equilibrium.What must be true for \(m\) such that the two strings attached to the piece of metal are almost horizontal?

The figure shows a truck pulling three crates across a rough road. Which of the following shows the directions of all the horizontal forces acting on crate 2?

Three blocks are stacked on top of one another. The top block has a mass of \( 4.6 \, \text{kg} \), the middle one has a mass of \( 1.2 \, \text{kg} \), and the bottom one has a mass of \( 3.7 \, \text{kg} \). Identify and calculate any normal forces between the objects.

A block hangs from the ceiling by a massless rope. A \( 3.0 \, \text{kg} \) block is attached to the first block and hangs below it on another piece of massless rope. The tension in the top rope is \( 63.0 \, \text{N} \).

When a horizontal force of \( 4.5 \, \text{N} \) acts on a block on a resistance-free surface, it produces an acceleration of \( 2.5 \, \text{m/s}^2 \). Suppose a second \( 4.0 \, \text{kg} \) block is dropped onto the first. What is the magnitude of the acceleration of the combination if the same force continues to act? Assume that the second block does not slide on the first block.

A block sliding down an frictionless inclined plane is experiencing both gravitational and normal forces; which force’s magnitude changes when the angle of the incline is increased?

In an experiment where a constant horizontal force pulls on a box across a rough floor starting from rest, what would happen to the acceleration of the box if its mass were doubled but the pulling force remained unchanged?

A ball falls straight down through the air under the influence of gravity. There is a retarding force\(F\) on the ball with magnitude given by\(F=bv\), where v is the speed of the ball and\(b\)is a positive constant. The ball reaches a terminal velocity after a time\(t\). The magnitude of the acceleration at time t/2 is

A simple Atwood’s machine remains motionless when equal masses \(M\) are placed on each end of the chord. When a small mass \(m\) is added to one side, the masses have an acceleration a. What is \(M\)? You may neglect friction and the mass of the cord and pulley.

Three blocks of masses 1.0, 2.0, and 4.0 kilograms are connected by massless strings, one of which passes over a frictionless pulley of negligible mass, as shown above. Calculate each of the following.

A 30 gram bullet is fired with a speed of 500 meters per second into a wall.

On a harsh winter day, a 1500 kg vehicle takes a circular banked exit ramp (radius R = 150 m; banking angle of 10 degrees) at a speed of 30 mph, since the speed limit is 35 mph. However, the exit ramp is completely iced up (= frictionless). To make matters worse, a wind is blowing parallel to the ramp in a downward direction. The wind exerts a force of 3000 N. Under these conditions, can the driver continue to follow a safe horizontal circle on the exit ramp and stay below the speed limit? To convert mph into m/s use 1 mi = 1607 m and 1 hr is 3600 s.

The block is moving horizontally at a constant velocity. There are two applied forces on the object as shown in the image. In which direction is the friction force acting on the object?

Why do raindrops fall with constant speed during the later stages of their descent?

A constant force of 8.0 N is exerted for 4.0 s on 16-kg object initially at rest. The change in speed of this object will be:

A car travels to right at constant velocity. The net force on the car is

A ring, seen from above, is pulled on by three forces. The ring if not moving. How big is the force F?

A crate rests on a horizontal surface and a woman pulls on it with a 10-N force. No matter what the orientation of the force, the crate does not move. Rank the surface on the crate, least to greatest.

The box is sitting on the floor of an elevator. The elevator is accelerating upward. The magnitude of the normal force on the box is