Exam 4: Forces and Newtons Laws of Motion

A 10-kg block is pushed against a vertical wall by a horizontal force of 100 N as shown in the figure. The coefficient of static friction, $\mu$ _s, between the block and the wall is 0.60; and the coefficient of kinetic friction, $\mu$ _k, is 0.40. Which one of the following statements is true, if the block is initially at rest?

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 minimum coefficient of static friction necessary to keep the top block from slipping on the bottom block?

A 2150-kg truck is traveling along a straight, level road at a constant speed of 55.0 km/h when the driver removes his foot from the accelerator. After 21.0 s, the truck's speed is 33.0 km/h. What is the magnitude of the average net force acting on the truck during the 21.0 s interval?

A net force is required to give an object with mass m an acceleration a. If a net force 6 is applied to an object with mass 2m, what is the acceleration on this object?

. The figure shows the free-body diagram for the block. represents the normal force on the block; and represents the force of kinetic friction. -If the coefficient of kinetic friction, , between the block and the surface is 0.30 and the magnitude of the frictional force is 80.0 N, what is the weight of the block?

What is the magnitude of the gravitational force acting on a 79.5-kg student due to a 58.0-kg student sitting 2.40 m away in the classroom?

Two satellites of different masses are in the same circular orbit around the earth. Which one of the following statements is true concerning the magnitude of the gravitational force that acts on each of them?

Two forces act on a 16-kg object. The first force has a magnitude of 68 N and is directed 24° north of east. The second force is 32 N, 48° north of west. What is the acceleration of the object resulting from the application of these two forces to the object?

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

Two 5-N boxes are attached to opposite ends of a spring scale and suspended from pulleys as shown. -What is the reading on the scale?

A rope holds a 10-kg rock at rest on a frictionless inclined plane as shown. -Determine the tension in the rope.

A 2.0-N force acts horizontally on a 10-N block that is initially at rest on a horizontal surface. The coefficient of static friction between the block and the surface is 0.50. -Suppose that the block now moves across the surface with constant speed under the action of a horizontal 3.0-N force. Which one of the following statements concerning this situation is false?

Three spring scales are attached along a straight line as shown. The scale on the left is attached to a wall. A force of 15 N is applied to the scale at the right. What is the reading on the middle scale?

A block is pulled at constant speed along a rough level surface by a rope that makes an angle of 30° with respect to the horizontal. The applied force along the rope is . The force of kinetic friction between the block and the surface is 10 N. -Which one of the following expressions gives the magnitude of the force11ec874c_df08_73b3_a44c_e7f94894d120_TB3413_11 in SI units?

A block is pulled at constant speed along a rough level surface by a rope that makes an angle of 30° with respect to the horizontal. The applied force along the rope is . The force of kinetic friction between the block and the surface is 10 N. -Which one of the following actions will increase the frictional force on the block?

A 10-kg block is connected to a 40-kg block as shown in the figure. The surface on that the blocks slide is frictionless. A force of 50 N pulls the blocks to the right. -What is the magnitude of the tension in the rope that connects the two blocks?

A 2.0-N force acts horizontally on a 10-N block that is initially at rest on a horizontal surface. The coefficient of static friction between the block and the surface is 0.50. -What is the magnitude of the frictional force that acts on the block?

A 8-kg block is set moving with an initial speed of 6 m/s on a rough horizontal surface. If the force of friction is 12 N, approximately how far does the block travel before it stops?

A rock is suspended from a string; and it accelerates downward. Which one of the following statements concerning the tension in the string is true?

A crate rests on the flatbed of a truck that is initially traveling at 15 m/s on a level road. The driver applies the brakes and the truck is brought to a halt in a distance of 38 m. If the deceleration of the truck is constant, what is the minimum coefficient of friction between the crate and the truck that is required to keep the crate from sliding?