Exam 5: Newtons Laws of Motion

Three boxes rest side-by-side on a smooth, horizontal floor. Their masses are 5.0 kg, 3.0 kg, and 2.0 kg, with the 3.0-kg mass in the center. A force of 50 N pushes on the 5.0-kg mass, which pushes against the other two masses. What is the contact force between the 5.0-kg mass and the 3.0-kg mass?

A locomotive is pulling three wagons along a level track with a force of 100,000 N. The wagon next to the locomotive has a mass of 70,000 kg, the next one, 50,000 kg, and the last one, 80,000 kg. Neglect friction. What is the force between the 80,000-kg and 50,000-kg wagons?

State Newton's third law of motion.

When you catch a ball, you feel a force against your hand. Why?

The mass of the Moon is about 1/80th of the mass of Earth. The force exerted by Earth on the Moon is about 80 times that exerted by the Moon on Earth.

A 1000-kg barge is being towed by means of two horizontal cables. One cable is pulling with a force of 80.0 N in a direction 30.0° west of north. The second cable pulls in a direction 20.0° east of north. What should the magnitude of its pulling force be so that the barge will accelerate northward?

A person has a mass of 45 kg. How much does she weigh on the Moon, where g = 1.62 m/s²?

A constant net force acts on an object. Describe the motion of the object.

To determine the mass of a car, a student (with a friend at the wheel) pushes the car holding a bathroom scale between himself and the car and carefully maintains a constant reading of 400 N on the scale while the car accelerates on level ground. At the conclusion of the experiment his friend reports that the car accelerated from rest to 14.0 km/hr in 12.0 s. What was the mass of the car?

Force is a vector quantity.

A block of mass M slides down a frictionless plane inclined at an angle θ with the horizontal. The normal reaction force exerted by the plane on the block is

A 20-ton truck collides with a 1500-lb car and causes a lot of damage to the car. Since a lot of damage is done on the car

An object is being acted upon by three forces and moves with a constant velocity. One force is 60.0 N along the x-axis, the second is 75.0 N along the y-axis. What is the magnitude of the third force?

A load is being lifted by means of two cables attached to it. The first cable exerts a force of 600 N at an angle of 35° to the left of the vertical. The second cable exerts a force of 1300 N. If the load is accelerating vertically, at what angle to the right of the vertical is the second cable pulling?

A catcher stops a ball traveling at 40 m/s in a distance of 20 cm and feels a force of 600 N against his glove. What is the mass of the ball?

A 47.0-kg person steps on a scale in an elevator. The scale reads 461 N. What is the elevator doing?

A 400-kg box is lifted vertically upward with constant velocity by means of two cables pulling at 40.0° on either side of the vertical direction. What is the tension in each cable?

A person has a mass of 45 kg. How much does she weigh?

You ride on an elevator that is moving downward with constant speed while standing on a bathroom scale. The reading on the scale is

A 40.0-kg box is being pushed along a horizontal, smooth surface. The pushing force is 15.0 N directed at an angle of 15.0° below the horizontal. What is the acceleration of the crate?