Exam 4: Forces and Newtons Laws of Motion

A rock is suspended from a string; and it moves downward at constant speed. Which one of the following statements is true concerning the tension in the string if air resistance is not ignored?

A rope holds a 10-kg rock at rest on a frictionless inclined plane as shown. -Determine the magnitude of the acceleration of the rock down the inclined plane if the rope breaks?

An astronaut orbits the earth in a space capsule whose height above the earth is equal to the earth's radius. How does the weight of the astronaut in the capsule compare to her weight on the earth?

Two sleds are hooked together in tandem as shown in the figure. The front sled is twice as massive as the rear sled. The sleds are pulled along a frictionless surface by an applied force . The tension in the rope between the sleds is . Determine the ratio of the magnitudes of the two forces, .

A physics student in a hot air balloon ascends vertically at constant speed. Consider the following four forces present in this situation: 11ec874b_21ea_ddf1_a44c_811fc40246c2_TB34225555_11 1= the weight of the hot air balloon 11ec874b_21ea_ddf1_a44c_811fc40246c2_TB34225555_11 3= the force of the student pulling on the earth 11ec874b_21ea_ddf1_a44c_811fc40246c2_TB34225555_11 2= the weight of the student 11ec874b_21ea_ddf1_a44c_811fc40246c2_TB34225555_11 4= the force of the hot air balloon pulling on the student -Which two forces form an "action-reaction" pair that obeys Newton's third law?

-Determine the magnitude of the acceleration of the spacecraft.

Two blocks rest on a horizontal frictionless surface as shown. The surface between the top and bottom blocks is roughened so that there is no slipping between the two blocks. A 30-N force is applied to the bottom block as suggested in the figure. -What is the force of static friction between the top and bottom blocks?

The figure shows the velocity versus time curve for a car traveling along a straight line. Which of the following statements is false?

A horse pulls a cart along a flat road. Consider the following four forces that arise in this situation. (1) the force of the horse pulling on the cart (2) the force of the cart pulling on the horse (3) the force of the horse pushing on the road (4) the force of the road pushing on the horse -Suppose that the horse and cart have started from rest; and as time goes on, their speed increases in the same direction. Which one of the following conclusions is correct concerning the magnitudes of the forces mentioned above?

. The figure shows the free-body diagram for the block. represents the normal force on the block; and represents the force of kinetic friction. -What is the magnitude of ?

Which one of the following statements concerning the two "gravitational constants" G, the universal gravitational constant, and g the magnitude of the acceleration due to gravity is true?

A block of mass M is hung by ropes as shown. The system is in equilibrium. The point O represents the knot, the junction of the three ropes. Which of the following statements is true concerning the magnitudes of the three forces in equilibrium?

A man stands on a spring scale in a moving elevator and notices that the scale reading is 20% larger than when he weighs himself in his bathroom. Which statement can not be true?

-The book has an acceleration of 0 m/s². Which pair of forces, excluding "action-reaction" pairs, must be equal in magnitude and opposite in direction?

An apple crate with a weight of 225 N accelerates along a frictionless surface as the crate is pulled with a force of 14.5 N as shown in the drawing. What is the horizontal acceleration of the crate?

A block of mass M is held motionless on a frictionless inclined plane by means of a string attached to a vertical wall as shown in the drawing. -If the string breaks, what is the magnitude of the acceleration of the block as it slides down the inclined plane?

A 2.0-kg object moves in a straight line on a horizontal frictionless surface. The graph shows the velocity of the object as a function of time. The various equal time intervals are labeled using Roman numerals: I, II, III, IV, and V. The net force on the object always acts along the line of motion of the object. -Which section(s) of the graph corresponds to a condition of zero net force?

Complete the following statement: The term net force most accurately describes

A rope holds a 10-kg rock at rest on a frictionless inclined plane as shown. -Which one of the following statements concerning the force exerted on the plane by the rock is true?

A 20-kg crate is suspended from a fixed, horizontal beam by two vertical ropes. What is the approximate tension in each rope?