1 ) A crate is at rest on the floor, and not in contact with any other objects.

Question

1 ) A crate is at rest on the floor, and not in contact with any other objects. Describe all the forces acting on the crate by identifying in each case the type of force, the direction of the force, and the external object exerting it on the crate. Don't list any of the forces the crate exerts on other objects.

2)An elevator is rising at a constant speed, subject only to the tension (FT) and gravitational (FG) forces exerted on it by the cable above it and the Earth, respectively. Use either Newton's First Law (N1L) or Newton's Second Law (N2L) of motion to explain why these two forces must have equal magnitudes (FT = FG).

3)The elevator in the previous question begins to slow down as it approaches the 8th floor. Use N2L (Newton's Second Law) to explain why, while elevator is slowing down, the gravitational force must have larger magnitude than the tension (FG > FT).

Explanation / Answer

1)

Floor in contact is exerting upward normal force to balance the weight of the crate.

Gravitational force is acting on the crate in downward direction.

Newton's Second Law: Nett Force = mass*acceleration => objects acceleration (rate of change of speed) in in the direction of nett force exerted.

2)

As per Newton's second law, if the net force on an object is zero => its speed will be constant

SInce the elevator is moving with a constant speed => tension and gravitational forces act in opposite directions and must be equal in magnitude as the elevator moves with constant speed.

3)

Elevator going up slows down => as per Newton's second law => magnitude of downward (retarding) force must be greater than that of tension (accelerating) force.

Related Questions

Navigate

• Browse (All)
• Browse 1
• Subjects

Integrity-first tutoring: explanations and feedback only — we do not complete graded work. Learn more.