PHYS101 Part 1

Which of the following quantities has units of a displacement? (There could be more than one correct choice.)

9.8 m/s2 40 km southwest 186,000 mi ** -120 m/s 32 ft/s2 vertically downward

Which of the following situations is impossible?

An object has constant non-zero acceleration and changing velocity. An object has constant non-zero velocity and changing acceleration. ** An object has velocity directed east and acceleration directed east. An object has zero velocity but non-zero acceleration. An object has velocity directed east and acceleration directed west.

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

Its acceleration is zero. Its acceleration is positive. ** Its acceleration is negative. Its acceleration is decreasing in magnitude as the car slows down.

You drive 4 km at 30 km/h and then another 4 km at 50 km/h. What is your average speed for the whole 8-km trip?

Less than 40 km/h. ** Equal to 40 km/h. More than 40 km/h. Not enough information.

A rock from a volcanic eruption is launched straight up into the air with no appreciable air resistance. Which one of the following statements about this rock while it is in the air is correct?

On the way up, its acceleration is downward and its velocity is upward, and at the highest point both its velocity and acceleration are zero. Throughout the motion, the acceleration is downward, and the velocity is always in the same direction as the acceleration. On the way down, both its velocity and acceleration are downward, and at the highest point both its velocity and acceleration are zero. The acceleration is downward at all points in the motion. ** The acceleration is downward at all points in the motion except that is zero at the highest point.

A ball is dropped from the top of a tall building. At the same instant, a second ball is thrown upward from the ground level. When the two balls pass one another, one on the way up, the other on the way down, compare the magnitudes of their acceleration:

The accelerations are in opposite directions. The acceleration of both balls is the same. ** The acceleration of the dropped ball is greater. The acceleration of the ball thrown upward is greater. The acceleration changes during the motion, so you cannot predict the exact value when the two balls pass each other.

At time t=0 an object is traveling to the right along the +x axis at a speed of 10.0 m/s with acceleration -2.0 m/s^2:

The object will continue to move to the right, slowing down but never coming to a complete stop. The object will slow down, eventually coming to a complete stop. The object will slow down, momentarily stopping, then pick up speed moving to the left. **

Two objects are thrown from the top of a tall building. One is thrown up, and the other is thrown down, both with the same initial speed. What are their speeds when they hit the street? Neglect air resistance.

The one thrown down is traveling faster. They are traveling at the same speed. ** The one thrown up is traveling faster. It is impossible to tell because the height of the building is not given.

You drop a rock off a bridge. When the rock has fallen 4 m, you drop a second rock. As the two rocks continue to fall, what happens to their velocities?

The velocity of the first rock increases faster than the velocity of the second. Both increase at the same rate. ** Both velocities stay constant. The velocity of the second rock increases faster than the velocity of the first.

An auto manufacturer advertises that their car can go "from zero to sixty in eight seconds." This is a description of what characteristic of the car's motion?

average speed displacement instantaneous speed instantaneous acceleration average acceleration **

Two objects are dropped from a bridge, an interval of 1.0 s apart. Air resistance is negligible. During the time that both objects continue to fall, their separation

decreases. stays constant. increases at first, but then stays constant. increases. ** decreases at first, but then stays constant.

A 10-kg rock and a 20-kg rock are thrown upward with the same initial speed v0 and experience no significant air resistance. If the 10-kg rock reaches a maximum height h, what maximum height will the 20-kg ball reach?

h ** 4h h/2 h/4 2h

A ball is thrown straight up, what are the velocity and acceleration of the ball at the highest point in its path?

v=0; a=0. v=9.8m/s up; a=0. v=0; a=9.8m/s2 up. v=9.8m/s down; a=0. v=0; a=9.8m/s2 down. **

When is the average velocity of an object equal to the instantaneous velocity?

when the velocity is constant ** always only when the velocity is decreasing at a constant rate only when the velocity is increasing at a constant rate never

A ball is thrown downward at a speed of 20 m/s. Choosing the +y axis pointing up and neglecting air resistance, which equation(s) could be used to solve for other variables? The acceleration due to gravity is g = 9.8 m/s2 downward.

y = y0+(−20m/s)t−(1/2)gt^2. v^2=(−20m/s)^2−2g(y−y0).

In which of the following cases does a car have a negative velocity and a positive acceleration? A car that is traveling in the:

−x direction at a constant 20 m/s. −x direction increasing in speed. +x direction decreasing in speed. +x direction increasing in speed. −x direction decreasing in speed. **