7.4-7.8 Unit PPT Quizizz Lesson

Multiple Choice

Consider a problem that asks for the distance of a fast-moving crate sliding across a factory floor and then coming to a stop. The most useful equation for solving this problem is

• $$F\ =\ ma$$  

• $$Ft\ =\ \Delta mv$$  

• $$KE\ =\ \frac{1}{2\ }mv^2$$  

• $$Fd\ =\ \Delta\ \frac{1}{2}mv^2$$  

Multiple Choice

The work done in bringing a moving car to a stop is the force of tire friction x stopping distance. If the initial speed of the car is doubled, the stopping distance is

• actually less.

• about the same.

• twice as far.

• None of the possible answers are correct.

Multiple Choice

Suppose the potential energy of a drawn bow is 50 joules and the kinetic energy of the shot arrow is 40 joules. Then

• energy is NOT conserved.

• 10 joules goes to warming the bow.

• 10 joules goes to warming the target.

• 10 joules are mysteriously missing.

Multiple Choice

In an ideal pulley system, a woman lifts a 100-N crate by pulling a rope downward with a force of 25 N. For every 1-meter length of rope she pulls downward, the crate rises

• 25 centimeters

• 45 centimeters

• 50 centimeters

• None of the answers are correct.

Multiple Choice

A certain machine is 30% efficient. This means the machine will convert

• 30% of the energy input to useful work -- 70% of the energy input will be wasted.

• 70% of the energy input to useful work -- 30% of the energy input will be wasted.

• Both answers are correct.

• Neither of the answers are correct.