Exam 8: Force

A stationary 1.67-kg object is struck by a stick.The object experiences a horizontal force given by F = at - bt²,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?

An object attached to an ideal massless spring is pulled across a frictionless surface.If the spring constant is 45 N/m and the spring is stretched by 0.88 m when the object is accelerating at 2.0 m/s²,what is the mass of the object?

A locomotive is pulling 19 freight cars,each of which is loaded with the same amount of weight.The mass of each freight car (with its load)is 37,000 kg.If the train is accelerating at 0.22 m/s² on a level track,what is the tension in the coupling between the second and third cars? (The car nearest the locomotive is counted as the first car,and friction is negligible.)

A construction worker pulls a box of tools on a smooth horizontal floor with a force of 100 N in a direction of 37.0° above the horizontal. The mass of the box and the tools is 40.0 kg. (a) Draw a free-body diagram for the box. (b) Calculate the acceleration of the box. (c) How hard does the floor push up on the box?

Two unequal masses M and m (M > m)are connected by a light cord passing over a pulley of negligible mass,as shown in the figure.When released,the system accelerates.Friction is negligible.Which figure below gives the correct free-body force diagrams for the two masses in the moving system?

A 10,000-kg rocket blasts off from earth with a uniform upward acceleration of 2.00 m/s² and feels no air resistance. The upward thrust force its engines must provide during this acceleration is closest to

A block of mass m = 8.40 kg,moving on a horizontal frictionless surface with a speed 4.20 m/s,makes a perfectly elastic collision with a block of mass M at rest.After the collision,the 8.40 block recoils with a speed of 0.400 m/s. In the figure,the blocks are in contact for 0.200 s.The magnitude of the average force on the 8.40-kg block,while the two blocks are in contact,is closest to

Two objects having masses m₁ and m₂ are connected to each other as shown in the figure and are released from rest.There is no friction on the table surface or in the pulley.The masses of the pulley and the string connecting the objects are completely negligible.What must be true about the tension T in the string just after the objects are released?

The figure shows two forces acting on an object,with magnitudes F₁ = 78 N and F₂ = 26 N.What third force will cause the object to be in equilibrium (acceleration equals zero)?

The International Space Station has a mass of 1.8 × 10⁵ kg. A 70.0-kg astronaut inside the station pushes off one wall of the station so she accelerates at 1.50 m/s². What is the magnitude of the acceleration of the space station as the astronaut is pushing off the wall? Give your answer relative to an observer who is space walking and therefore does not accelerate with the space station due to the push.

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?

15)Bumpers on cars are not of much use in a collision.To see why,calculate the average force a bumper would have to exert if it brought a 1200-kg car (a so-called compact model)to a rest in 15 cm when the car had an initial speed of 2.0 m/s (about 4.5 mph).(Bumpers are built with springs that compress to provide a stopping force without,hopefully,denting the metal.)

Consider what happens when you jump up in the air.Which of the following is the most accurate statement?

On a horizontal frictionless floor,a worker of weight 0.900 kN pushes horizontally with a force of 0.200 kN on a box weighing 1.80 kN.As a result of this push,which statement could be true?

Point P in the figure indicates the position of an object traveling at constant speed clockwise around the circle.Which arrow best represent the direction the object would travel if the net external force on it were suddenly reduced to zero?

Which of the graphs in the figure illustrates Hooke's Law?

A block is on a frictionless horizontal table,on earth.This block accelerates at 3.6 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/s². A horizontal force of 45 N is applied to the block when it is on the moon.What acceleration does this force impart to the block?

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/s².What is the weight of the block on the moon?

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?

In order to lift a bucket of concrete,you must pull up harder on the bucket than it pulls down on you.