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Exam 4: Applying Newtons Laws

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Question 61

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A velocity vector has components 36 m/s westward and 22 m/s northward.What are the magnitude and direction of this vector?

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42 m/s at ...

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Question 62

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The figure shows a system consisting of three blocks,a light frictionless pulley,and light connecting ropes that act horizontally on the upper two blocks.The 9.0-kg block is on a perfectly smooth horizontal table.The surfaces of the 12-kg block are rough,with µ_k = 0.30 between the 12-kg and 9.0-kg blocks.The mass M of the hanging block is set so that it descends at a constant velocity of 3.25 m/s. (a)What is the mass M of the hanging block? (b)The mass M is now changed to 5.0 kg,causing it to accelerate downward after it is released.What is the acceleration of the hanging block?

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(a)3.6 kg ...

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Question 63

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If a vector's components are all negative,then the magnitude of the vector is negative.

A 40-kg box is being pushed along a horizontal smooth surface.The pushing force is 15 N directed at an angle of 15° below the horizontal.What is the magnitude of the acceleration of the crate?

A 55-kg box rests on a horizontal surface.The coefficient of static friction between the box and the surface is 0.30.A horizontal 140-N force is exerted on the box.What is the friction force exerted by the surface on the box?

Three blocks,light connecting ropes,and a light frictionless pulley comprise a system,as shown in the figure.An external force of magnitude P is exerted downward on block A,causing block A to accelerate downward at a constant 2.5 m/s².The rope connecting block B and block C exerts a 60-N force. (a)What is the magnitude of the force P? (b)What is the mass of block C?

A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal.If we can neglect air,what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

A player hits a tennis ball into the air with an initial velocity of 32 m/s at 35° from the vertical.How fast is the ball moving at the highest point in its trajectory if effects of air are negligible?

Two blocks,A and B,are being pulled to the right along a horizontal surface by a horizontal 100-N pull,as shown in the figure.Both of them are moving together at a constant velocity of 2.0 m/s to the right,and both weigh the same. Which of the figures below shows a correct force diagram of the horizontal forces exerted on the upper block,A?

Two boxes are connected to each other by a string as shown in the figure.The 10-N box slides without friction on the horizontal table surface.The pulley is ideal and the string has negligible mass.What is true about the tension force T that the string exerts on the boxes?

A projectile leaves the ground at 150 m/s and reaches a maximum height of 0.57 km.If there was no air,at what angle above the horizontal did it leave the ground?

A 200-g hockey puck is launched up a ramp that is inclined at a 30° angle above the horizontal.The coefficients of static and kinetic friction between the puck and the ramp are µ_s = 0.40 and µ_k = 0.30,respectively,and the puck's initial velocity at the base is 3.8 m/s parallel to the sloping surface of the ramp.What speed does the puck have when it slides back down to its starting point?

A person throws a ball horizontally from the top of a building that is 24.0 m above the ground level.The ball lands 100 m down range from the base of the building.What was the initial velocity of the ball? Neglect air and use g = 9.81 m/s².

A 150-N crate is being pulled up a perfectly smooth ramp that slopes upward at 15° by a pull that is directed at 30° above the surface of the ramp.What is the magnitude of the pull required to make the crate move up the ramp at a constant velocity of 1.75 m/s?

A policeman investigating an accident measures the skid marks left by a car on the horizontal road.He determines that the distance between the point that the driver slammed on the brakes (thereby locking the wheels) and the point where the car came to a stop was 28.0 m.From a reference manual he determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300.How fast was the car going when the driver applied the brakes?

The free-fall acceleration on the Moon is only one-sixth of that on Earth,and the Moon has no atmosphere.If you hit a baseball on the Moon with the same effort (and therefore at the speed and angle) as on Earth,how far would the ball would travel on the Moon compared to on Earth? Neglect effects of air on Earth.

A ball is thrown at an original speed of 8.0 m/s at an angle of 35° above the horizontal.If there is no air,what is the speed of the ball when it returns to the same horizontal level?

An object slides on a level floor.It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s².What is the coefficient of kinetic friction between the object and the floor?

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal.What must be true about the force of static friction f exerted on the block?

When rolled down a mountainside at 7.0 m/s,the horizontal component of its velocity vector was 1.8 m/s.What was the angle of the mountain surface above the horizontal?