Exam 4: Newtons Laws

Figure 4.7 -The leg and cast in Fig. 4.7 have mass m_leg = 30 kg. Determine the mass of object m₂ and the angleè for the system in balance. Mass m₁ = 10 kg and ö = 30°.

Figure 4.9 The figure shows two objects of masses m₁ and m₂ placed on two inclined surfaces of different angles, è₁ and è₂. The connection between the masses is a taut, massless string running over a massless and frictionless pulley. -In Fig. 4.9, the masses are m₁= 10 kg and m₂ = 20 kg, and the incline angles are è₁ = 30° and è₂ = 50°. What are the magnitude and the direction of acceleration of the system and the tension in the string if the coefficient of friction for the surface under m₁ is ì₁ = 0.30 and under m₂ it is ì₂ = 0.40.

A student in an elevator is checking Newton's laws using a scale. The elevator moves upward with decreasing speed. Is the scale showing a reading that is larger or less than the student's actual weight?

You exercise with a 5.0 kg dumbbell. You need to accelerate it downward with an acceleration of 3.0 m/s². What are the magnitude and the direction of the force you need to push with?

You charge a balloon by rubbing it on your hair and it sticks to the ceiling by electrostatic force. Which of these four free body diagrams describes all the forces acting on the balloon? The forces are labelled as follow: is the weight of the balloon, is electrostatic force, and is a normal force.

Although a body is moving, net force acting on it can be zero.

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 = 3 kg and m = 5 kg. What is the minimum coefficient of static friction between the horizontal surface and M such that the system is NOT moving?

A car goes around a banked curve of radius 1.2 km and with angle è = 4°. What is the safest speed (in km/h) going around the curve if the road is icy?

The coefficient of static friction between a seal and a steep rock is 0.8. What is the steepest incline angle of a rock that the seal can lie on without slipping?

Figure 4.6 ​ ​ ​ The figure shows a hanging body. The chords are massless. -In Fig. 4.6, an alpinist with mass M = 80 kg is hanging between a wall and the ceiling of a cave. If the rope is manufactured to withstand tension T = 500 N, is it sufficiently strong to hold the alpinist?

A student in an elevator is checking Newton's laws using a scale. The elevator moves downward with decreasing speed. The scale is showing a reading larger than the student's actual weight.

Figure 4.2 Two crates connected by a string passed through a pulley. -Two weights, one with mass 2 kg and the other with mass 4 kg, are attached to the ends of a massless string that hangs over an ideal pulley. The system is allowed to move freely. What is the value of acceleration of the system?

The utricular macula in the inner ear detects angular acceleration of human head.

You jump off an airplane and fall freely for a while (before you open a parachute). Which of these statements describes what is happening in this situation?

Mass is a measure of inertia of a body.

A child holds a ball in her hand. Which of these forces is opposite but equal in magnitude to the weight of the ball?

If you are riding on a bus and the bus stops abruptly, you feel a tendency to go forward. There is a force that occurs at that moment pushing you forward.

Figure 4.8 The figure shows an object on an inclined surface. -In Fig. 4.8, the object has a mass M = 5.0 kg, and the incline angle is è = 40°. What is the minimum force needed to prevent the body from sliding down if the coefficient of static friction between an object and the incline surface ì = 0.3?

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, mass m₁= 5 kg and incline angles are è₁ = 30° and è₂ = 50°. Both inclines are smooth frictionless surfaces. What is the value of m₂ if the system is NOT moving?

Two flying squirrels of roughly the same size but with different masses, m₁ = 110 g and m₂ = 180 g, fly from a high tree. What is the ratio of terminal velocities v₁ and v₂ for the two squirrels?