Chapter 8 Motion and Forces SPEED DESCRIBES HOW FAST AN OBJECT MOVES How do you determine speed? Take the distance traveled by an object and the time it takes to travel that distance SI UNIT FOR SPEED: meters/second or m/s What is constant speed? When an object covers equal distance in equal amounts of time EQUATION d÷t

What is the difference between speed and velocity? Velocity describes both speed and direction Velocity changes if speed or direction Change Or both d v t

Warm up problems Anna swims exactly 220 m toward the shore in 62 s. What is her velocity? Daniel throws a baseball 32 m/s from third to first base in 1.2 s. What is the distance from first to third for the ball? Bilal is an olympic skier who finished his first 5.2 km race at an average velocity of 56 m/s downhill. What was his time in seconds?

What is momentum Product of an object’s mass and its velocity What happens to the momentum as the mass increases? So does its momentum What is the law of Conservation of momentum? The total amount of momentum in a system is conserved.

Comparison of velocity and momentum

Equation for momentum p=m x v

Warm up problems for momentum Katara with a mass of 63.o kg runs with a constant forward velocity of 1.50 m/s. What is her momentum? Ben hits a baseball with a momentum of 5.06 kg.m/s away from home plate after being hit. The ball weighs 1.35 kg. What is the velocity of the ball? What is the mass of a toddler who is riding in a car moving east at 89 km/h with a momentum of 220 kg/m/s east.

What is acceleration? Or a = ∆v t Change in velocity divided by the time interval in which the change occurs What is the acceleration equation for straight line motion? acceleration = final velocity – initial velocity time Or a = ∆v t

Examples of Si units of measurement that follow ……. Mass (m)= kg (g or lbs or ounces) Distance (d)= m or km (miles, ft, inches) Time (t) = s or hr (minutes, days, yrs) Velocity (v) = m/s or km/hr (ft/s, mph) Momentum (p) = kg. m/s

Warm up problems for acceleration Natalie accelerates her bike along a straight path for 0 m/s to 4.0 m/s in 2.5 s. Find her final acceleration A cyclist travels at a constant velocity of 5.0 m/s westward, then speeds up with a steady acceleration of 2.0 m/s2. Calculate the cyclist speed after acceler. for 5.0 s. A flowerpot falls off a second-story windowsill with a velocity of 14.7 m/s. The acceleration for this fall due to gravity is 9.8 m/s2. How long does it take for the pot to hit the sidewalk?

What is Force? What is Net Force? The cause of acceleration or change in an object’s velocity. What is Net Force? The combination of all forces acting on an object

How does force affect the motion of an object? force will cause on object to change its velocity or acceleration. Distinguish between balanced and unbalanced forces? Balanced forces: equal amount of force exerted so net force is zero No movement…..cancel each other Unbalanced forces: forces acting on object do not have same strength, so greatest force will cause the object to accelerate in that direction.

What is the difference between balanced and unbalanced forces? Balanced forces: equal amount of force exerted so net force is zero No movement…..cancel each other Unbalanced forces: forces acting on object do not have same strength, so greatest force will cause the object to accelerate in that direction.

How does friction affect the motion of an object? unbalanced force that acts against an objects direction of motion Also provides the force needed to balance the force of gravity on an object that isn’t moving.

What is air resistance? A form of friction that opposes an ojbects motion This is caused by the interaction between the surface of a moving object and the air molecules. What affects air resistance The size of the object The shape of the object Speed the object moves

The attraction between two particles of matter due to their mass. What is gravity? The attraction between two particles of matter due to their mass.

What affects gravitational force? Mass and distance The greater the mass of an object=the larger the gravitational force it exerts on the other. If the distance between two objects is doubled, the gravitational force bewteen them decreases to ¼ its original value If the distance is tripled, the gravitational force decreases to o1/9 its original value

What are Newton’s three laws of motion 1st law: an object at rest remains at rest and an object in motion mantains its velocity unless acted upon by an unbalanced force 2nd law: The unbalanced force acting on an object equals the object’s mass times its acceleration 3rd law: For every action force, there is an equal and opposite reaction force.