Exam 3: Newtonian Mechanics

In the figure,a 10-lb weight is suspended from two spring scales,each of which has negligible weight.Which one of the following statements about the readings in the scales is true?

A 75-N box rests on a perfectly smooth horizontal surface.The minimum force need to start the box moving is

When a 45-kg person steps on a scale in an elevator,the scale reads a steady 410 N.Which of the following statements must be true? (There could be more than one correct choice.)

An object is falling on Earth close to its surface.Earth exerts a force of W magnitude on the object.The magnitude of the force that the object exerts on Earth is

You are standing in a moving bus,facing forward,when you suddenly slide forward as the bus comes to an immediate stop.What force caused you to slide forward from the point of view of the observer on the ground?

A truck is using a hook to tow a car whose mass is one quarter that of the truck.If the force exerted by the truck on the car is 6000 N,then the force exerted by the car on the truck is

An elevator suspended by a vertical cable is moving downward but slowing down. The force that the cable exerts on the elevator must be

A 75-N object is pulled on a horizontal surface by a horizontal pull of 50 N to the right.The friction force exerted on this object is 30 N to the left.What is the acceleration of the object?

The figure shows a graph of acceleration-versus-sum of the forces exerted on a 125-g object.What should be the value of the first tick-mark on the vertical scale,as indicated by the arrow in the figure?

You pull on a crate with a rope.If the crate moves,the rope's pull on the crate must have been larger than the crate's pull on the rope,but if the crate does not move,both of these pulls must have been equal.

During a hard stop,a car and its passengers slow down with an acceleration of 8.0 m/s².What magnitude force does a 50-kg passenger exert on the seat belt in such a stop?

As shown in the figure,a woman is straining to lift a large crate,but without success because it is too heavy.We denote the forces exerted on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person,C is the magnitude of the contact force being exerted on the crate by the floor perpendicular to the floor,and W is the the force that Earth exerts on the crate.How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

A golf club hits a golf ball with a force of 2400 N,sending the ball into the air.The force exerted on the club by the ball must be less than 2400 N or else the ball would not have moved forward.

When a 45-kg person steps on a scale in an elevator,the scale reads a steady 480 N.Which of the following statements must be true? (There could be more than one correct choice.)