science 3

The unit of force is __________.

. One newton = 1 kg · m/s2

Gravity exerts an

unbalanced force on the ball, changing the direction of its path from only forward to forward and downward.

According to Newton's second law, if the acceleration is zero, then the net force on the box is zero.

Another force that cancels your push must be acting on the box.

Friction

Friction is the force that opposes the sliding motion of two surfaces that are touching each other. The amount of friction between two surfaces depends on two factorsthe kinds of surfaces and the force pressing the surfaces together.

What causes friction?

Friction results from the sticking together of two surfaces that are in contact.

Gravity is an attractive force between any two objects and depends on __________

Gravity is an attractive force between any two objects and depends on the masses of the objects and the distance between them.

Gravity

Gravity is an attractive force between any two objects that depends on the masses of the objects and the distance between them.

The momentum of an object doesn't change unless its mass, velocity, or both change.

Momentum, however, can be transferred from one object to another.

Newton's first law

Newton's first law of motion states that the motion of an object changes only if an unbalanced force acts on the object.

Newton's second

Newton's second law of motion describes how the forces exerted on an object, its mass, and its acceleration are related.

Rolling Friction

Rolling friction is the frictional force between a rolling object and the surface it rolls on. -Static friction acts over the deformed area where the wheel and surface are in contact, producing a frictional force called rolling fiction.

Recall that acceleration is the change in velocity divided by the time it takes for the change to occur.

So, a hard-thrown ball has a greater acceleration than a gently thrown ball

If it takes the same amount of time to throw both balls, the softball would have less acceleration.

The acceleration of an object depends on its mass as well as the force exerted on it. Force, mass, and acceleration are related.

Which of the following equations represents the law of universal gravitation? A. F = G(m1m2/d2) B. G = F(m1m2/d2) C. F = G(m1 - m2/d2) D. F = G(d2/m1m2)

The answer is A. In the equation, G is the universal gravitational constant and d is the distance between the two masses, m1 and m2.

Which is NOT one of the four basic forces? A. gravity B. net C. strong nuclear D. weak nuclear

The answer is B. The fourth basic force is the electromagnetic force, which causes electricity, magnetism, and chemical interactions between atoms and molecules.

The momentum of an object is the product of its __________ and __________. A. mass, acceleration B. mass, velocity C. mass, weight D. net force, velocity

The correct answer is B.

If you throw a softball and a baseball as hard as you can, why don't they have the same speed?

The difference is due to their masses.

weight.

The gravitational force exerted on an object is called the object's

centripetal force.

The net force exerted toward the center of a curved path is called a

Terminal Velocity

The terminal velocity is the highest speed a falling object will reach. -The terminal velocity depends on the size, shape, and mass of a falling object.

If two surfaces are in contact, welding or sticking occurs where the bumps touch each other.

These microwelds are the source of friction.

When you throw a ball, the force exerted by your hand pushes the ball forward.

This force gives the ball horizontal motion. No force accelerates it forward, so its horizontal velocity is constant, if you ignore air resistance

Newton's second law also can be used to calculate the net force if mass and acceleration are known.

To do this, the equation for Newton's second law must be solved for the net force, F.

What's different about throwing a ball horizontally as hard as you can and tossing it gently?

When you throw hard, you exert a much greater force on the ball. The hard-thrown ball has a greater change in velocity, and the change occurs over a shorter period of time.

Newton's third law of motion

describes action-reaction pairs this way. When one object exerts a force on a second object, the second one exerts a force on the first that is equal in strength and opposite in direction.

Static friction

friction is the frictional force that prevents two surfaces from sliding past each other.

In this equation G , and d is the , m1 and m2.

is a constant called the universal gravitational constant -is the distance between the two masses

Sliding Friction

is the force that opposes the motion of two surfaces sliding past each other.

However, when you let go of the ball, gravity can pull

it downward, giving it vertical motion.The ball has constant horizontal velocity but increasing vertical velocity.

momentum

of an object is the product of its mass and velocity.

Air Resistance

opposes the motion of objects that move through the air Air resistance causes objects to fall with different accelerations and different speeds

According to Newton's third law of motion, what happens when one object exerts a force on a second object?

According to Newton's law, the second object exerts a force on the first that is equal in strength and opposite in direction.

When two objects collide, what happens to their momentum?

According to the law of conservation of momentum, if the objects in a collision exert forces only on each other, their total momentum doesn't change, even when momentum is transferred from one object to another.

Action and Reaction Forces Don't Cancel

According to the third law of motion, action and reaction forces act on different objects Thus, even though the forces are equal, they are not balanced because they act on different objects.

Close to Earth's surface, the acceleration of a falling object in free fall is about

9.8 m./s2 This acceleration is given the symbol g and is sometimes called the acceleration of gravity

centripetal acceleration.

Acceleration toward the center of a curved or circular path is called

Newton's second law of motion states that _________ of an object is in the same direction as the net force on the object.

Acceleration can be calculated by dividing the net force in newtons by the mass in kilograms.

No matter how far apart two objects are, the gravitational force between them never completely goes to zero.

Because the gravitational force between two objects never disappears, gravity is called a long-range force.

acceleration is the difference

between the initial and final velocity, divided by the time.