PSAE – Day 2 - ISBE Science Test          Review of Physics Concepts           

Involving Force and MotionStandard 12 D

Peggy Piper, Lincoln Way North High School

Grayslake North Scienceand

12.11.74 ~ F=ma, Action/Reaction

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Force And Motion

12.11.74 ~ F=ma, Action/Reaction

But...

Force And Motion

12.11.74 ~ F=ma, Action/Reaction

12.11.74 ~ Conservation of Momentum

Force And Motion

Momentum stays constant!Only the ball has momentum (mass x velocity) before the collision. After the collision, the ball loses momentum (slows down) and Jocko gains momentum (speeds up) to keep the total momentum constant!

12.11.74 ~ Conservation of Momentum

Force And Motion

12.11.75 ~ Inertia

An astronaut in outer space away from gravitational or frictional forces throws a rock. The rock will ………..

Force And Motion

12.11.75 ~ Inertia

….continue on forever in a straight line!!Newton’s 1st Law (Law of Inertia) says objects will not change their speed or direction unless there is an outside force.

Force And Motion

12.11.76 ~ Simple Machines

If you are able to push your end of a lever down a distance of 1 meter using 10 N of force, how high can you lift an 100 N boulder on the other end?

100 N

??

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12.11.76 ~ Simple Machines

The amount of work you put in (force x distance) must equal the amount of work you get out. You multiplied your force by ten, so you decreased your distance by 1/10th.

100 N

1/10 m

To gain the greatest mechanical advantage, increase your distance from the fulcrum and the distance you have to push

Force And Motion

12.11.77 ~ Buoyancy

Force And Motion

12.11.77 ~ Buoyancy

The block displaces its weight in water as long as it floats, if it’s too dense to float, it displaces less than its weight, it displaces its volume instead.

Force And Motion

d

12.11.77 ~ Bernoulli

Water with air bubbles flows through a pipe thatgets narrower. In the narrow region, the water gains speed and the bubbles are;

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12.11.77 ~ Bernoulli

As the water’s speed increases, pressure decreases (Bernoulli' s principle). Decreased water pressure squeezes less on air bubbles.

If the flowing water continues its flow into a wider section of pipe, speed decreases, pressure increases, and the bubbles become smaller.

Force And Motion

12.11.78 ~ Gravity

Force And Motion

12.11.78 ~ Gravity

Force And Motion

Answer d, nothing changes!!! Newton’s Law of Gravitation says that gravitation pull is based on the two masses and their distance apart – not their volume!!

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12.11.79 ~ Frame of Reference

Suppose you are standing in the aisle of a bus traveling along a straight road at 100 km/h, and you hold a pencil above your head.

What happens to the pencil if you let go?

Force And Motion

12.11.79 ~ Frame of Reference

The pencil drops straight down in front of you!!

The pencil is traveling at 100 km/hr relative to the road…………… but it is traveling at 0 km/hr relative to you and the bus!

Force And Motion

12.11.79 ~ Circular Motion

You are swinging a ball in a circle above your head. What happens when the string breaks?

Force And Motion

12.11.79 ~ Circular Motion

The answer is C! The ball will fly in a straight line tangent to the circle.

The inward force from the string was causing the ball to accelerate towards the middle.

This is what Earth would do if there was no gravitational pull from the sun!

Force And Motion

12.11.80 & 81 ~ Electrical Force

 

When you rub a balloon on your head, you can then make it stick to the wall. How does this work?

Force And Motion

12.11.80 & 81 ~ Electrical Force

The balloon becomes “charged” with electrons that transfer from your hair. When the charged surface is placed near the wall, the electrons in the wall move away leaving a positively charged surface. The two opposite charges attract.

Force And Motion

The electrical force holding the balloon to the wall beats the gravitational force pulling the balloon to the ground!!