Assignment 3: Newtons second and third laws of motion – Flashcards

The direction of the force of friction on a sliding crate is _______.

How does the force of friction for a sliding object vary with speed?

If Dr. Hewitt applies 3 N of force to keep the block moving at a steady rate, what must be the force of friction, and why?

You are dragging a block on a surface with friction at a steady speed of 2 m/s and exert a force of 5 N to do so. What is the force of friction? Why?

What general rule can you conclude about the force needed to keep an object in motion at a steady rate?

Which depends on gravity?

In the string-pull illustration in Figure 4.8, a sharp jerk on the bottom string results in the bottom string breaking. Does this occur because of the ball's weight or its mass?

Fill in the blanks: The Standard International unit for mass is _____. The Standard International unit for force is _____.

If the mass of a sliding block is somehow tripled at the same time the net force on it is tripled, how does the resulting acceleration compare with the original acceleration?

Air resistance on a parachutist at terminal speed _______.

What is the net force that acts on a 10-N falling object when it encounters 4 N of air resistance? When it encounters 10 N of air resistance?

In the absence of air resistance, if a ball is thrown vertically upward with a certain initial speed, on returning to its original level it will have the same speed. When air resistance is a factor, will the ball be moving faster, the same, or more slowly than its throwing speed when it gets back to the same level? Why? (Physicists often use a "principle of exaggeration" to help them analyze a problem. Consider the exaggerated case of a feather, not a ball, because the effect of air resistance on the feather is more pronounced and therefore easier to visualize.)

What happens to the weight reading on a scale you stand on when you toss a heavy object upward?

A boxer cannot exert much force on a piece of tissue paper suspended in air because _______.

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

Consider the system of a single football. If you kick it, is there a net force to accelerate the system? If a friend kicks it at the same time with an equal and opposite force, is there a net force to accelerate the system?

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

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

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

Which of Newton's three laws focuses on interactions?

If you stand next to a wall on a frictionless skateboard and push the wall with a force of 50

If your mass is 80 kg , find your acceleration.

In a tug-of-war between Sam and Maddy, each pulls on the rope with a force of 250 N. What is the tension in the rope? If both remain motionless, what horizontal force does each exert against the ground?

Within a book on a table, there are billions of forces pushing and pulling on all the molecules. Why is it that these forces never by chance add up to a net force in one direction, causing the book to accelerate "spontaneously" across the table?

When you rub your hands together, can you push harder on one hand than the other?

Two 100-N weights are attached to a spring scale as shown. Does the scale read 0, 100, or 200 N, or does it give some other reading? (Hint: Would it read any differently if one of the ropes were tied to the wall instead of to the hanging 100-N weight?)