Exam 1

For general projectile motion, the horizontal component of a projectiles acceleration

) is zero

A student kicks a soccer ball in a high arc toward the opponentȇs goal. At the highest point in its trajectory:

) neither the ballȇs velocity nor its acceleration is zero

An Olympic athlete throws a javelin at four different angles above the horizontal, each with the same speed: 30°, 40°, 60°, and 80°.ȱȱWhich two throws cause the javelin to land the same distance away?

30° and 60°

Ball is thrown straight up and when it reaches the top of flight a second ball is thrown straight up. When do their paths cross?

Above h/2

If an object is accelerating toward a point, then it must be getting closer and closer to that point.

False

If the acceleration of an object is negative, the object must be slowing down.

False

) A monkey is sitting at the top of a tree 20 m above ground level. A person standing on the ground wants to feed the monkey. He uses a bow and arrow to launch the food to the monkey. If the monkey remains seated at the top of the tree, how should the person aim the arrow containing the food so that the monkey gets the food?

He should aim it above the monkey.

Suppose that an object is moving with constant nonzero acceleration. Which of the following is an accurate statement concerning its motion?

In equal times its velocity changes by equal amounts

When a football in a field goal attempt reaches its maximum height, how does its speed compare to its initial speed?

It is less than its initial speed.

Suppose that a car traveling to the west (the -x direction) begins to slow down as it approaches a traffic light. Which statement concerning its acceleration in the x direction is correct?

Its acceleration is positive but its velocity is negative.

For general projectile motion, which statement is true when the projectile is at the highest point of its trajectory?

Its velocity is perpendicular to the acceleration.

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. Compare the time it takes each to reach the lake below.

James and John will reach the surface of the lake at the same time.

Drop 2 rocks 4m apart

Separation increases

If the graph of the position as a function of time for an object is a horizontal line, that object cannot be accelerating

True

There is an uncertainty associated with every measurement

True

A pilot drops a bomb from a plane flying horizontally at a constant speed.ȱȱNeglecting air resistance, when the bomb hits the ground the horizontal location of the plane will

be over the bomb.

For a projectile launched horizontally, the vertical component of its velocity

continuously increases.

You are trying to cross a river that flows due south with a strong current.ȱȱYou start out in your motorboat on the west bank desiring to reach the east bank directly east from your starting point. You should head your motorboat

in a northeasterly direction.

A package of supplies is dropped from a plane, and one second later a second package is dropped. Neglecting air resistance, the distance between the falling packages will

increase

does displacement depend on the location of origin on a coordinate system?

no

When can we be certain that the average velocity of an object is always equal to its instantaneous velocity?

only when the velocity is constant

For a projectile launched horizontally, the horizontal component of a projectileȇs velocity

remains a non-zero constant.

For general projectile motion, the horizontal component of a projectiles velocity

remains a non-zero constant.

For general projectile motion, the vertical component of a projectiles acceleration

remains a non-zero constant.

A ball rolls off the edge of a table. The horizontal component of the ballȇs velocity remains constant during its entire trajectory because

the ball is not acted upon by a force in the horizontal direction.

James and John dive from an overhang into the lake below. James simply drops straight down from the edge. John takes a running start and jumps with an initial horizontal velocity of 25 m/s. When they reach the lake below,

the splashdown speed of John is larger than that of James