Physics and Simple Machines Flashcards

Power is defined as:

Answer: The rate at which work is done

Power = Work / Time, measuring how quickly energy is transferred or work is done, expressed in watts (W).

An object at rest remains at rest unless acted upon by an unbalanced force. This describes:

Answer: Newton's First Law (inertia)

Newton's First Law, also called the law of inertia, states that objects resist changes in their state of motion.

A block-and-tackle system uses 5 rope segments to support a load. What is its ideal mechanical advantage?

Answer: 5

In a block-and-tackle system, the ideal MA equals the number of rope segments supporting the load, which is 5.

When a ball is thrown upward, its kinetic energy at the peak of its trajectory is:

Answer: Zero

At the peak, the ball momentarily stops (velocity = 0), so kinetic energy (½mv²) equals zero; all energy has converted to potential energy.

The efficiency of a machine is defined as:

Answer: (Useful work output / Work input) × 100%

Efficiency measures what fraction of input energy does useful work, always less than 100% due to friction and other losses.

A hydraulic jack multiplies force by having a small piston with area 2 cm² and a large piston with area 20 cm². What force does the large piston exert if 100 N is applied to the small piston?

Answer: 1000 N

Pascal's principle: F_large / A_large = F_small / A_small, so F_large = 100 N × (20/2) = 1000 N.

Momentum is conserved in a collision between two objects when:

Answer: No external net force acts on the system

Conservation of momentum applies whenever the net external force on a system is zero, regardless of collision type.