Understanding Forces: Contact and Non-contact

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Questions and Answers

A stationary box requires a 150N force to initiate movement across a concrete floor. Once in motion, a force of 120N is sufficient to maintain constant velocity. What explains this difference in required force?

Fluid friction assists the motion once the box begins to slide.
The coefficient of sliding friction is greater than the coefficient of static friction.
The initial force overcomes static friction, which is generally higher than sliding friction. (correct)
The force of gravity increases once an object is in motion, thus reducing the required force.

Consider two objects, one with twice the mass of the other, separated by a certain distance. If the distance between them is doubled, how does the gravitational force change?

It doubles.
It is reduced to one-eighth of the original force. (correct)
It is reduced to one-fourth of the original force.
It halves.

An astronaut is performing a repair on the exterior of the International Space Station. Which of the following forces is primarily responsible for keeping the astronaut and their tools from floating away into space?

The magnetic force exerted by the Earth's magnetic field.
The combined gravitational force of the Earth and the Moon.
The gravitational force between the astronaut/tools and the Earth. (correct)
The static friction between the astronaut's boots and the space station.

A car is traveling at a constant speed on a level road. Which statement best describes the forces acting on the car?

The applied force from the engine is equal to the opposing forces of friction and air resistance. (C) Signup and view all the answers

How would an object's weight and mass change if it were transported from Earth to a planet with twice the mass and half the radius of Earth?

Weight would be eight times greater, mass would remain the same. (A) Signup and view all the answers

A book rests on a table. Which of the following statements accurately describes the forces acting in this situation?

The book exerts a downward force on the table, and the table exerts an equal and opposite upward force on the book; these forces are action-reaction pairs, but do not balance each other. (C) Signup and view all the answers

A skydiver jumps from a plane. Initially, their acceleration is high, but as they fall, their acceleration decreases until they reach terminal velocity. Which of the following best explains why the skydiver's acceleration decreases?

The force of air resistance increases as the skydiver's velocity increases, eventually equaling the force of gravity. (B) Signup and view all the answers

Two identical blocks are connected by a string. One block is placed on a horizontal surface, and the string is passed over a pulley to hang the other block vertically. Assuming the surface is frictionless, what will be the acceleration of the blocks?

Half of g, since the weight of one block is accelerating both blocks. (D) Signup and view all the answers

A satellite is orbiting Earth at a constant altitude. If the satellite suddenly fires its engines in the direction opposite to its motion, what will initially happen to its speed and altitude?

Both speed and altitude will decrease. (D) Signup and view all the answers

A car's tires have a static friction coefficient of 0.8 with dry pavement and 0.4 with wet pavement. If the car is traveling at the same speed on both surfaces, how does the maximum possible deceleration (stopping power) compare between dry and wet conditions?

The maximum deceleration is twice as high on dry pavement as on wet pavement. (B) Signup and view all the answers

Flashcards

Force

A push or pull on an object, measured in Newtons (N).

Contact Force

A force that requires direct contact between objects.