HW 5

One end of a rope is pulled with 100 N, while the opposite end also is pulled with 100 N. The tension in the rope is

100 N

a soccer player kicks a ball with 1500 N of force. the ball exerts a reaction force against the player's foot of

1500 N

Two people, one twice as massive as the other, attempt a tug-of-war with 12 meters of rope on frictionless ice. After a brief time, they meet. The heavier person slides a distance of

4 m. the magnitude of the force is the same for both, but as F=ma, the twice as heavy person has 1/2 the acceleration

A top view of an airplane shows it being blown off course by the wind in three different directions. Use a pencil and the parallelogram rule to sketch the vectors showing the resulting velocities for each case. (Figure 1) Rank the speeds from fastest to slowest.

B (bc force of wind is pushing at a diagonal) A (bc force is pushing to side) C (bc force is pushikng back)

Because the forces that act on a cannonball and the recoiling cannon from which it is fired are equal in magnitude, why are the accelerations of both so different?

F = ma. the canon has a much greater mass than the cannonball, so the canon accelerates less with the same amount of force.

state two forms of Newton's third law of motion:

For every action, there is an equal and opposite reaction., Whenever one object exerts a force on a second object, the second object exerts an equal and opposite force on the first.

terminal speed

NO acceleration

How does the magnitude of acceleration of the rifle compare with the magnitude of acceleration of the bullet, and why?

The acceleration of the rifle is smaller than the acceleration of the bullet. They experience the same magnitude of force, but the mass of the rifle is greater, and so the rifle will experience a smaller acceleration than the bullet.

An orange, a wheeled trolley, and an apple are placed inside a dotted rectangle that represents a system. The trolley and the apple are on a horizontal floor. The orange sits at the top of the trolley. The trolley is pulled rightward via a horizontal string by the apple. Two dashed vectors pointing in opposite directions are displayed on the string. One vector points from the apple, to the left, and the other vector points from the orange, to the right., identify the force that accelerates the apple-orange system.

a friction force acting on the apple's feet

Force vector components for a sled pulled horizontally by a rope at an upward angle:

are normally at right angles to each other.

Newton's 3rd law

equal and opposite force, action-reaction

terminal velocity

falling objects direction + speed

In the apple-pulling-the orange sequence in this chapter, what is the force that accelerates the system across the floor?

friction between the apple and the floor.

Fill in the blanks: Newton's first law is often called the law of ____; Newton's second law is the law of ____; and Newton's third law is the law of ____.

inertia; acceleration; action-reaction

When you step off a curb, Earth pulls you downward and you pull Earth upward. Why do you not sense the Earth moving toward you?

it moves, but by an imperceptible amount

Can you push on a wall without the wall pushing back on you?

no, because your push is a part of the interaction with the wall.

Can you physically touch a person without that person touching you with the same amount of force?

no, when you touch a person they must touch you with equal and opposite force.

The team to win in a tug-of-war is the team that

pushes harder on the floor while holding the rope.

How does the distance traveled by the bullet compare with the distance traveled by the rifle in the same time, and why?

the bullet will travel further than the rifle due to its greater acceleration

The force that propels a rocket is that provided by: decreased mass. energetic reactions as the fuel is burned. ejected fuel. the expelled gas pushing on the rocket

the expelled gas pushing on the rocket. exhaust gases are pushed backward, and the exhaust gases push the rocket forward.

How does a helicopter get its lifting force?

the helicopter exerts a downward force on the air; the reaction forces of the air are called lift.

What happens to the magnitude of the normal vector on a block resting on an incline when the angle of the incline increases?

the magnitude of the normal vector decreases.

How does the force on the rifle compare with the force on the bullet, and why?

the magnitude of the rifle is equal to the magnitude of the bullet and opposite in direction, because for every action there is equal and opposite reaction

A small car and a large truck have a head-on collision. Which of the following statements is true? The greater force acts on the truck. The greater force acts on the car. The magnitudes of both forces are the same. Both forces are identical.

the magnitudes of both forces are the same. action/reaction forces are equal in magnitude and opposite in direction

A boxer cannot exert much force on a piece of tissue paper suspended in air because: there is little follow-through with the punch. the tissue lacks enough strength. the tissue paper has too little mass to exert much force on the boxer's fist. the time of the interaction is too brief

the tissue paper has too little mass to exert force on the boxer's fist. therefore, the opposite forces are very small.

What specific force is accelerating Nellie (Figure 5.23 in the textbook) down the hill? (assume friction to be neglectable)

the x-component force of gravity. once weight (mg) is resolved we can see that mgx, the specific force acting in the direction of motion.

Earth pulls on the moon. Similarly the moon pulls on Earth, evidence that

these 2 comprise an action-reaction pair

A small insect hits your windshield while you are driving in the highway. How do you compare the magnitude and direction of the force exerted by the car on the insect versus the force of the insect on the car? They have the same magnitude and opposite directions. They are opposite and the car exerts a higher force on the bug .They are equal and in the same direction. They are equal and perpendicular to each other.

they have the same magnitude and opposite directions.

How many forces are required for an interaction? Two forces, a contact force and a friction force, are needed for an interaction. One force, an action, is needed for an interaction. Two forces, an action and a reaction, are needed for an interaction. One force, a reaction, is needed for an interaction.

two forces, an action and a reaction are needed for an interaction

To produce a net force on a system, must there be an externally applied net force?

yes, there must be an external force

Earth pulls down on you with a gravitational force that you call your weight. Do you pull up on Earth with the same amount of force?

yes, you pull up on Earth with the same force.