Physics I Concept Questions: Exam 1

As compared to Jack, Jill does twice the work in half the time. Jill's power output is

Four times Jack's power output

A mass is attached to one end of a string. The other end of the string is attached to a rigid support. The mass is released at A and swings in a vertical arc to points B, C, and D, as shown. At what point does the mass have its highest speed

Point C, straight down

A simple pendulum, consisting of a mass (m), and a string of length (l), swings upward making an angle theta with the vertical. The work done by the tension force is

Zero

Work done by STATIC FRICTION is always

Zero

A person carries a mass of 10kg and walks along the +X axis for a distance of 100m with a constant velocity of 2m/s. What is the work done by this person

Zero Joules

An acorn falls from a tree. Compare its kinetic energy, to its potential energy

K increases and U decreases

Is it possible for a system to have negative potential energy

Yes, since the choice of the zero potential energy is arbitrary

If vector A has components Ax > 0 and Ay > 0, then the angle that this vector makes with the positive x-axis must be in the range

0*-90*

An object is moving with constant non-zero VELOCITY in the +X axis. The VELOCITY versus time graph of this object is

A horizontal straight line

An object is moving with constant non-zero ACCELERATION in the +X axis. the POSITION versus time graph of this object is

A parabolic curve

An object is moving with constant non-zero ACCELERATION in the +X axis. The VELOCITY versus time graph of this object is

A straight line making an angle with the time axis

An object is moving with constant non-zero VELOCITY in the +X axis. The POSITION versus time graph of this object is

A straight line making an angle with the time axis

Which if any of the following statements concerning the work done by a conservation force is NOT true

All of these statements are true

Two stones, one of mass M and the other of mass 2M, are thrown directly upward with the same velocity at the same time form ground level and feel no air resistance. Which statement about these stones are true

At its highest point, the heavier stone will have twice as much gravitational potential energy as the lighter one because it is twice as heavy

If the position versus time graph of an object is a horizontal line, the object is

At rest

Suppose a ball is thrown straight up, reaches maximum height, then falls to its initial height. Select the correct statement about the direction of the velocity and acceleration as the ball is going down

Both its velocity and its acceleration point downward

That which is under the curve in a velocity versus time graph represents

Displacement

A dog is standing in the bed of a truck. The bed is coated with ice, causing the force of friction between the dog and the truck to be zero. The truck is initially at rest, and then accelerates to the right, moving along a flat road. As seen from a stationary observer (watching the truck move to the right), the dog

Does not move left or right, but the back of the truck moves towards the dog

The stretch of a spring and the force it exerts are inversely proportional

False

When an object is in its translation equilibrium, the net force acting on the object is non-zero

False

You swing a bat and hit a heavy box with a force of 1500N. The force the box exerts on the bat is

Exactly 1500N whether or not the box moves

A body moving with constant speed cannot be accelerating

False

A car is being towed at constant velocity on a horizontal road using a horizontal chain. The tension in the chain must be equal to the weight of the car in order to maintain constant velocity

False

An object moving along a curved path with constant speed does not have a net force acting on it

False

In order to get an object moving, you must push harder on it than it pushes back on you

False

If the net work done on an object is positive, then the object's kinetic energy

Increases

An object is moving to the right, and experiencing a net force that is directed to the right. The magnitude of the force is decreasing with time. The speed of the object is

Increasing

When an object experiences uniform circular motion, the direction of the net force is

Is directed toward the center of the circular path

For general projectile motion, the horizontal component of a projectile's acceleration

Is zero

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

A stone is thrown straight up. When it reaches its highest point

Its velocity is zero and its acceleration is not zero

Suppose a ball is thrown straight up, reaches maximum height, then falls to its initial height. Select the correct statement about the direction of the velocity and acceleration as the ball is going up

Its velocity points upward and its acceleration points downward.

A ball drops some distance and loses 30J of gravitational potential energy. Do NOT ignore air resistance. how much kinetic energy did the ball gain?

Less than 30J

In the absence of an external force, a moving object will

Move with constant velocity

If the velocity versus time graph of an object is a straight line making an angle of 30* with the time axis, the object is

Moving with constant non-zero acceleration

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

Neither the ball's velocity nor its acceleration is zero

You are standing in a moving bus, facing forward, and you suddenly fall forward as the bus comes to an immediate stop. The force acting on you that causes you to fall forward is

No forces were acting on you to cause you to fall

Can work be done on a system if there is no motion

No, since work involves a non-zero displacement

For general projectile motion, the horizontal component of a projectile's velocity

Remains a non-zero constant

For general projectile motion, the vertical component of a projectile's acceleration

Remains a non-zero constant

If you push twice as hard against a stationary brick wall, the amount of work you do

Remains constant at zero

When a car goes around a curve, it has a tendency to skid outwards. Is the frictional force between the tires and the ground that keeps the car from skidding kinetic or static

Static

A 20-ton truck collides with a 1500lb car and causes a lot of damage to the car. During the collision

The force of the truck due to the collision is exactly equal to the force on the car

Two objects, one of mass (M) and other of mass (2M) are dropped from the top of a building. When they hit the ground

The heavier one will have twice the kinetic energy of the lighter one

If the acceleration vector of an object is directed anti-parallel to the velocity vector

The object is slowing down

If the acceleration vector of an object is directed parallel to the velocity vector

The object is speeding up

If the acceleration vector of an object is directed perpendicular to the velocity vector

The object is turning

Consider a plot of the displacement (X) as a function of the applied force (F) for an ideal elastic spring. The slope of the curve would be

The reciprocal of the spring constant

A girl throws a stone from a bridge, consider the following ways she might throw the stone. The speed of the stone as it leaves her hand is the same in each case, and air resistance is negligible Case 1: thrown straight up Case 2: thrown straight down Case 3: thrown 45* horizontal Case 4: straight horizontally

The speed will be the same in all cases

A ball is tossed vertically upward. When it reaches its highest point (before falling back downward)

The velocity is zero, the acceleration is directed downward, and the force of gravity acting on the ball is directed downward

A net horizontal force is required for a body to move in a horizontal circle

True

An ideal pulley changes the direction of the tension in a string without changing its magnitude

True

If a force always acts perpendicular to an object's direction of motion, that force cannot change the objects kinetic energy

True

The force of static friction between two surfaces in parallel to the surface of contact, and in the direction that opposes relative motion

True

The force of static friction between two surfaces is independent of the area of contact between the surfaces

True

Vector quantities are represented in terms of their magnitude and direction

True

When an object is solely under the influence of conservation of forces, the sum of its kinetic and potential energies does not change

True

Swimmers at a water park have a choice of two friction-less water slides. Although both slides drop over the same height, h, slide 1 is straight while slide 2 is curved, dropping quickly at first and leveling out. How does the speed of swimmer 1 compare to the speed of swimmer 2 at the end of the slide

V1 = V2

Consider what happens when you jump up in the air. Which of the following is the most accurate statement

When you push down on the earth with a force greater than your weight, the earth will push back with the same magnitude force and thus propel you into the air

On a force vs. position graph, the area under curve is a representation of

Work