Newton's Laws and Collisions

Newton's Laws and Collisions

Review

Forces

• A force is a push or a pull

• A force can be contact or noncontact

• Noncontact forces include magnetic, gravity, electric.

• Contact forces include friction, normal force, air resistance, and applied forces.

• When forces acting on one object are balanced, the object remains at rest or in constant motion.

• When forces acting on an object are unbalanced, there will be change in velocity.

Multiple Select

Which of the follow are contact forces?

• friction

• gravity

• normal force

• air resistance

• electric force

Newton's First Law

• An object in motion tends to stay in motion unless acted upon by an unbalanced force.

• An object at rest tends to stay at rest unless acted upon my an unbalanced force.

• The first law is often called the law of inertia.

• Inertia means that an object usually resist a change in motion. The more mass an object has, the more inertia it has. For example, a train has more inertia than feather.

Newton's Second Law

• F= m * a

• m=F/a

• a = F/m

• The more mass an object has, the more force is needed to accelerate it. The more force you apply, the more it will accelerate. There are a lot of applications of Newton's Second Law.

Newton's Third Law

• For every action, there is an equal and opposite reaction.

• Often called action, reaction force pairs.

• An example might include a flying plane. The applied force pushes it forward, but air resistance pushes back with an equal and opposite force.

• All forces are found in pairs!

Multiple Choice

This word means an object's resistance to change in motion.

• unbalanced force

• balanced force

• inertia

• Newton

Multiple Choice

If we apply a force of 10 Newtons to each of the following pieces of clay, which one will accelerate the most?

• 1 gram piece of clay.

• 0.5 gram piece of clay

• 3 gram piece of clay

• 2 gram piece of clay

Multiple Choice

Which of Newton's Laws best describes inertia?

• 1

• 2

• 3

• 4

Multiple Choice

If a magician pulls a table cloth off a table really fast, the dishes can remain in place if they magician pulls quickly enough. What law does this demonstrate?

• Newton's 1st law

• Newton's 2nd law

• Newton's 3rd law

Balanced forces

When a skateboarder pushes the ground, the ground pushes back with an equal but opposite force. If the forces are equal and opposite, why does the skater accelerate?

Balanced forces

The skateboarder accelerates because the forces are acting on different objects. The applied force is being applied to the ground, and the friction force is being applied to the skater, accelerating him.

Momentum=mass * velocity. It is measured using (kg*m/s). If all of the vehicles are going the same speed, which one has the most momentum?

Multiple Choice

Which of the following has the highest momentum?

• A 10kg ball going 50 km/hr.

• A 20 kg ball going 25 km/hour

• A 2 kg ball going 250 km/hr.

• A 101kg ball going 5 km/hr.

Collisions

• Simple collisions can be elastic or inelastic

• Some collisions are more complex, such as when a crumple zone in a car crumples up.

• Elastic collisions see only a small change in the kinetic energy. For example, the happy ball was very bouncy.

• Inelastic collisions see a loss of kinetic energy. The energy is converted to different forms.

Conservation of momentum

• states that momentum is neither created nor destroyed, but only changed through the action of forces as described by Newton's laws of motion.

• 
  

• 
  

• 
  

Multiple Choice

A 100-kilogram ball is traveling at 2 m/s, and a 25-kilogram ball is traveling at 10 m/s. Which ball has the greater momentum?

• The 100 kg ball

• The 25 kg ball.

Multiple Choice

Traveling back to G.E.S. from Overnight Camp took approximately 4 hours. The camp is about 180 kilometers away. What was our average velocity if we were traveling Northeast the whole time?

• 25 km/hr

• 45 km/hr

• 720 km/hr

• 22 km/hr

Use the formula to find average acceleration.

• Vf is your final velocity.

• Vi is the starting velocity.

• t is time.

Multiple Choice

A lizard accelerates from 2 m/s to 10 m/s in 4 seconds. What is the lizard’s average acceleration?

• 2 m/s/s

• -3 m/s/s

• 7 m/s/s

• 3 m/s/s/