Exam 4: Newtons Laws

Figure 4.3 The figure shows two objects of masses m₁ and m₂, placed on two inclined surfaces of different angles è₁ and è₂. The connection between masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.3, the two masses are the same (m₁ = m₂ = 10 kg); the incline angles are è₁ = 30° and è₂ = 50°. What are the magnitude and direction of the acceleration of the system, and the tension in the string, if both inclined surfaces are frictionless?

A truck has a crate in its cargo bed. If the truck stops abruptly and the crate does not move, the direction of the frictional force that the floor of the cargo bed exerts on the crate is backward.

A car goes around a banked curve of radius 1.2 km at a constant speed of 95 km/h. If no friction is required, at what angle should the curved portion be banked?

A student in an elevator is checking Newton's laws using a scale. The scale is showing a reading lower than the student's actual weight. Which one of these statements explains this phenomenon?

If you are riding on a bus and the bus stops abruptly, you feel a tendency to go forward. Is there a force that occurs at that moment pushing you forward? Describe the concept.

A truck has a crate in its cargo bed. If the truck accelerates forward and the crate does NOT move, in which of these directions is the frictional force that the floor of the cargo bed exerts on the crate?

A sled is gliding down an incline with angleè. In the absence of friction, what component of the weight is driving the sled downward?

If an object is at rest, its velocity has to be zero.

Figure 4.5 The figure shows a body hanging by two identical light cords. -In Fig. 4.5, an alpinist with mass M = 80 kg is hanging between a wall and the ceiling of a cave. If angle è = 30°, is the rope, which was manufactured to withstand tension T = 2000 N, sufficiently strong to hold the alpinist?

Figure 4.11 -Fig. 4.11 illustrates an otolith near the membrane surface of the utricular macula, with the head tilted sideways by angle è. Dendrites near the otolith illustrate the geometry of the otolith-membrane-dendrite interaction. Sketch the free body diagram with three forces acting on it: its weight the normal force and a force parallel to the surface layer of the otolithic membrane Give the reasoning behind your choice of any coordinate system chosen.

A squid moves through the water by means of ejecting a water jet. Explain, according to Newton's third law, the relationship between the direction of the water jet and the direction of the squid's motion.

Which of the following statements include all the essential elements of Newton's first law?

Which one of these forces produces centripetal acceleration of a car on a flat circular track?

If a car stays parked on an inclined street without slipping, its total weight is balanced by the static friction force between the tires and the street.

The force of friction is parallel to the surface along which the body moves and opposite to the direction of motion.

A seal is sunbathing on an inclined rock, and NOT slipping. Which one of these statements correctly describes the normal force?

Figure 4.4 The figure shows two bodies of masses M and m, M placed on a horizontal surface and m hanging at the side, connected by a light cord over a massless and frictionless pulley. -In Fig. 4.4, the masses are M = 10 kg and m = 20 kg. The coefficient of friction for the horizontal surface is ì = 0.4. What are the acceleration of the system and the tension in the string?

Figure 4.3 The figure shows two objects of masses m₁ and m₂, placed on two inclined surfaces of different angles è₁ and è₂. The connection between masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.3, masses are m₁= 10 kg and m₂ = 15 kg; incline angle is è₁ = 30°. What is the value of è₂ if the system is NOT moving?

You are moving in an elevator with constant speed, on the way up. Which of these statements correctly describes the normal force exerted by the floor of the elevator on you?

You push a desk with force and the desk does not move. Force is one force in a pair of interaction forces. The other force is the friction force the floor exerts on you.