Exam 4: Forces and Newtons Laws of Motion

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. -What is the magnitude of the tension in the string?

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 of the graph corresponds to the application of the largest constant net force?

A rock is suspended from a string; and it accelerates upward. Which statement is true concerning the tension in the string?

At a playground, a child slides down a slide that makes a 42° angle with the horizontal direction. The coefficient of kinetic friction for the child sliding on the slide is 0.20. What is the magnitude of her acceleration during her sliding?

A marble is dropped straight down from a distance h above the floor. Let F_m = the magnitude of the gravitational force on the marble due to the earth; F_e = the magnitude of the gravitational force on the earth due to the marble; A_m = the magnitude of the acceleration of the marble toward the earth; A_e = the magnitude of the acceleration of the earth toward the marble. Which set of conditions is true as the marble falls toward the earth? Neglect any effects of air resistance.

A spring scale is fastened to the ceiling of a railway car. When a 1.0-kg block is hung from the scale, it reads 12 N and is oriented as shown in the figure. What is the approximate acceleration of the car as measured by an observer at rest on the ground outside of the car?

Two forces act on a 4.5-kg block resting on a frictionless surface as shown. What is the magnitude of the horizontal acceleration of the block?

In a tug-of-war, each man on a 5-man team pulls with an average force of 500 N. What is the tension in the center of the rope?

A woman stands on a bathroom scale in an elevator that is not moving. The scale reads 500 N. The elevator then moves downward at a constant velocity of 5 m/s. What does the scale read while the elevator descends with constant velocity?

pulls on a crate of mass m that is in contact with a rough surface. The figure shows the magnitudes and directions of the forces that act on the crate in this situation. represents the weight of the crate. represents the normal force on the crate, and represents the frictional force. -What is the magnitude of , the normal force on the crate?

-Which one of the following statements concerning this situation is true?

A 4-kg block is connected by means of a massless rope to a 2-kg block as shown in the figure. Complete the following statement: If the 4-kg block is to begin sliding, the coefficient of static friction between the 4-kg block and the surface must be

Two 5-N boxes are attached to opposite ends of a spring scale and suspended from pulleys as shown. -Suppose that the system were placed in an elevator that accelerates downward at 2 m/s². What would the scale read?

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

A small plane climbs with a constant velocity of 240 m/s at an angle of 24° with respect to the horizontal. Which statement is true concerning the magnitude of the net force on the plane?

-Which two forces form an "action-reaction" pair that obeys Newton's third law?

The graph shows the velocities of two objects of equal mass as a function of time. Net forces F_A, F_B, and F_C acted on the objects during intervals A, B, and C, respectively. Which one of the following choices is the correct relationship between the magnitudes of the net forces?

A 2.00-kg projectile is fired at an angle of 20.0°. What is the magnitude of the force exerted on the projectile when it is at the highest position in its trajectory? Neglect any effects of air resistance.

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. -In which section of the graph is the magnitude of the net force decreasing?

When the net force that acts on a hockey puck is 12 N, the puck accelerates at a rate of 48 m/s². Determine the mass of the puck.