Chapter 4

Two forces are exerted on an object Two forces are exerted on an object. What third force would make the net force point to the left? STT4.1

Two forces are exerted on an object Two forces are exerted on an object. What third force would make the net force point to the left? STT4.1

Gravity, acting downward. The normal force, acting upward. You’ve just kicked a rock, and it is now sliding across the ground about 2 meters in front of you. Which of these forces act on the ball? Gravity, acting downward. The normal force, acting upward. The force of the kick, acting in the direction of motion. Friction, acting opposite the direction of motion. A, B and D but not C. STT4.2

Gravity, acting downward. The normal force, acting upward. You’ve just kicked a rock, and it is now sliding across the ground about 2 meters in front of you. Which of these forces act on the ball? Gravity, acting downward. The normal force, acting upward. The force of the kick, acting in the direction of motion. Friction, acting opposite the direction of motion. A, B and D but not C. STT4.2

Two rubber bands stretched the standard distance cause an object to accelerate at 2 m/s2. Suppose another object with twice the mass is pulled by four rubber bands stretched the standard length. The acceleration of this second object is 1 m/s2 . 2 m/s2 . 4 m/s2 . 8 m/s2 . 16 m/s2 . STT4.3

Two rubber bands stretched the standard distance cause an object to accelerate at 2 m/s2. Suppose another object with twice the mass is pulled by four rubber bands stretched the standard length. The acceleration of this second object is 1 m/s2 . 2 m/s2 . 4 m/s2 . 8 m/s2 . 16 m/s2 . STT4.3

Three forces act on an object Three forces act on an object. In which direction does the object accelerate? STT4.4

Three forces act on an object Three forces act on an object. In which direction does the object accelerate? STT4.4

An elevator suspended by a cable is moving upward and slowing to a stop. Which free-body diagram is correct? STT4.5

An elevator suspended by a cable is moving upward and slowing to a stop. Which free-body diagram is correct? STT4.5

A Martian lander is approaching the surface A Martian lander is approaching the surface. It is slowing its descent by firing its rocket motor. Which is the correct free-body diagram for the lander? STT5.1

A Martian lander is approaching the surface A Martian lander is approaching the surface. It is slowing its descent by firing its rocket motor. Which is the correct free-body diagram for the lander? STT5.1

Rank order, from largest to smallest, the size of the friction forces to in these 5 different situations. The box and the floor are made of the same materials in all situations. fc > fd > fe > fb > fa. fb > fc > fd > fe > fa. fa > fc = fd = fe > fb. fa = fb > fc = fd = fe. fb > fc = fd = fe > fa. STT5.3

Rank order, from largest to smallest, the size of the friction forces to in these 5 different situations. The box and the floor are made of the same materials in all situations. fc > fd > fe > fb > fa. fb > fc > fd > fe > fa. fa > fc = fd = fe > fb. fa = fb > fc = fd = fe. fb > fc = fd = fe > fa. STT5.3

The terminal speed of a Styrofoam ball is 15 m/s The terminal speed of a Styrofoam ball is 15 m/s. Suppose a Styrofoam ball is shot straight down with an initial speed of 30 m/s. Which velocity graph is correct? STT5.4

The terminal speed of a Styrofoam ball is 15 m/s The terminal speed of a Styrofoam ball is 15 m/s. Suppose a Styrofoam ball is shot straight down with an initial speed of 30 m/s. Which velocity graph is correct? STT5.4

Chapter 4 Reading Quiz

More than your true weight. Less than your true weight. An elevator that has descended from the 50th floor is coming to a halt at the 1st floor. As it does, your apparent weight is More than your true weight. Less than your true weight. Equal to your true weight. Zero. STT5.2

More than your true weight. Less than your true weight. An elevator that has descended from the 50th floor is coming to a halt at the 1st floor. As it does, your apparent weight is More than your true weight. Less than your true weight. Equal to your true weight. Zero. STT5.2

The weight excluding the container What is a “net force?” The weight excluding the container The vector sum of all forces in a problem The vector sum of all forces acting on an object The vector force applied by a net The vector sum of all forces that add up to zero IG4.1

The weight excluding the container What is a “net force?” The weight excluding the container The vector sum of all forces in a problem The vector sum of all forces acting on an object The vector force applied by a net The vector sum of all forces that add up to zero IG4.1

is another name for the law of inertia. Newton’s third law is another name for the law of inertia. says that the velocity of an object is determined by the net force on the object. says that every action has an equal and opposite reaction. was not discussed in this chapter. IG4.4

is another name for the law of inertia. Newton’s third law is another name for the law of inertia. says that the velocity of an object is determined by the net force on the object. says that every action has an equal and opposite reaction. was not discussed in this chapter. IG4.4

The coefficient of static friction is smaller than the coefficient of kinetic friction. equal to the coefficient of kinetic friction. larger than the coefficient of kinetic friction. not discussed in this chapter. IG5.3

The coefficient of static friction is smaller than the coefficient of kinetic friction. equal to the coefficient of kinetic friction. larger than the coefficient of kinetic friction. not discussed in this chapter. IG5.3