ch3 dynamic FT

An object will remain at rest or in uniform motion unless it is acted upon by a net force. This statement is a direct consequence of which of Newton's laws of motion?

• Newton's first law

• Newton's second law

• Newton's third law

• the law of gravitation

An object of mass m is sliding down a frictionless inclined plane that makes an angle θ with the horizontal. What is the magnitude of the object's acceleration?

• g

A 5.0 kg block is pulled across a horizontal surface by a horizontal rope with a tension of 20.0 N. The kinetic friction force opposing the motion is 5.0 N. What is the acceleration of the block?

• 5 m/s²

• 4 m/s²

• 3 m/s²

• 2 m/s²

A hockey puck slides on a frictionless ice surface. Which of the following statements is true regarding its motion?

• the puck's acceleration is directly proportional to its velocity

• the puck will continue to move at a constant velocity

• a constant force is required to keep the puck moving at a constant velocity

• the puck will eventually slow down due to its own inertia

A 10.0 kg box is pulled with a force of 50.0 N at an angle of 30∘ above the horizontal. A kinetic friction force of 15.0 N opposes the motion. What is the magnitude of the normal force on the box?

• 50 N

• 73 N

• 49 N

• 24.5 N

A ball is thrown straight up into the air. Ignoring air resistance, what is the direction of the net force on the ball at the very top of its flight?

• upward

• downward

• zerp

• the direction is undefined, as the velocity is momentarily zero

A 2.0 kg block is on a horizontal surface with a coefficient of static friction μs​=0.40 and a coefficient of kinetic friction μk​=0.20. What is the minimum horizontal force required to start the block moving?

• 3.92 N

• 19.6 N

• 7.84 N

• 0 N

A book rests on a table. According to Newton's Third Law, the action-reaction pair to the force of gravity exerted by the Earth on the book is:

• the friction force between the book and the table

• the force of gravity exerted by the book on the Earth

• the force of the book on the table

• the normal force exerted by the table on the book

A 1.0 kg box is held against a vertical wall. A force of 20.0 N is applied horizontally to the box. The coefficient of static friction between the box and the wall is μs​=0.60. What is the magnitude of the friction force acting on the box?

• 9.8 N

• 20.0 N

• 12.0 N

• 5.88 N

A box is pushed across a rough horizontal floor at a constant velocity. Which of the following statements is true?

• the net force on the box is zero

• the force of kinetic friction is greater than the pushing force

• the pushing force is greater than the force of kinetic friction

• the net force on the box is in the direction of motion