Physics Quiz 1

One force vector has (x,y ) components (5N, 3N) and a second has (x,y) components (2N, 2N) . Both forces act on the same object. These forces produce a net force with components ________ and ________

(7N, 5N); 8.6 N

In how many of the following situations does the car have a westward acceleration?

1

Consider the following five graphs (note the axes carefully). Which of these represent one dimensional motion at constant acceleration, including a=0 ?1

1, 2 , 4 and 5

The magnitude of the force vector (x,y) components (5N, 5N) is:

7.1

A ball is launched up a ramp by a spring as shown in the figure. At the time when the clock starts, the ball is near the bottom of the ramp and rolling up the ramp as shown. It goes to the top and then rolls back down. For the graphs shown below, the horizontal axis represents the time. The vertical axis is unspecified. Select then number of the graph that could accurately represent: 1. The x component of the ball's position 2. The x component of the ball's velocity 3. The x component of the ball's acceleration

8, 3, 2

A. Can two force vectors of unequal magnitude sum to zero net force? B. Can three force vectors of equal magnitude sum to zero net force?

A. no, they must have equal magnitude and move in opposite directions to cancel out. B. Yes, but in addition to equal magnitude, they must have opposite directions.

A ball is fired by a cannon from the top of the cliff as shown in the figure below. Which of the path would the cannonball mot closely follow?

B

Two pitchers are standing side by side, and simultaneously throw baseballs a and b. The balls follow the parabolic trajectories shown. Which of the following statements are true?

Ball B hits the ground before Ball A.

An object's motion is restricted to one dimension along the positive x-axis. It stays to the right of the origin. Answer each of the questions below by selecting the velocity versus time graph that is the best choice to describe the answer. i) Which velocity graph shows an object moving away from the origin with constant velocity?(ii) Which velocity graph shows an object at rest?(iii) Which velocity graph shows an object moving toward the origin with constant velocity? (iv) Which velocity graph shows an object changing direction?

C, G, D, E

A skier skis in a straight line down a hill gradually picking up speed as he goes. Which of the following could plausibly be an external force diagram for the skier during this motion ? Assume air resistance is negligible.

Diagram D: acceleration is not a force. A normal force is acting upon the skier.

A bullet is fired horizontally from a rifle on the moon (no air, g=1.6 m/s^2) with initial speed v0. Assuming a level and endless ground, which statement is FALSE? The bullet moves along a parabolic path During the flight, the minimum speed of the bullet is v0. The flight time increases as v0 increases. During its entire flight the acceleration is constant.

During the flight time increases as v0 increases.

The positions of two blocks at successive 0.20 second time intervals are represented by the numbered squares in the figure below.

In terms of position v time, the upper block do not have a constant velocity, and are moving away from the point of origin. Therefore, they are accelerating. However, since the blocks on the bottom are moving at a constant velocity, then they are not accelerating.

Look at the position versus time graph below. Do A and B ever have the same speed?

No, A and B never have the same speed.

Which of the following statements about velocity and/or speed are always TRUE? 1 Velocity is a vector quantity and and speed is a scalar quantity . 2. The average velocity of an object on a round trip journey would be zero 3. Person X moves from location A to location B in 5 seconds .Person Y moves between the same two locations in 10 seconds. The speed of person X is twice that of person Y 4. Person X moves from location A to location B in 5 seconds. Person Y moves between the same two locations in 10 seconds. The velocity of person X is twice that of person Y .

Only statements 1, 2, and 4 are correct.

Which of the following statements about displacement are TRUE? 1. Distance is a vector quantity and displacement is a scalar quantity 2. If a person walks in a straight line and never changes direction then the distance and the magnitude of the displacement are exactly the same. 3. The diagram below depicts the path of a person walking from position A to B back to C then to D. The distance traveled is 90 yards. 4. For the same diagram below, the displacement of the person walking from A to B to C to D is 50 yards.

Only statements 2 and 3 are true

In an inertial frame, an object cannot remain at rest unless which of the following holds? The net force acting on it is zero. The net force acting on it is constant. There are no forces at all acting on it. There is only one force acting on it.

The net force acting on it is zero ?

A box is at rest on a flat table. Which of the following is true ?

The normal force and the gravitational force are equal in magnitude and opposite in direction.

An object is thrown straight up. At the top of its path

The velocity is zero and the acceleration is equal to g pointing down (-)

Is it possible to have motion in the absence of a net force?

Yes

Is it possible to have motion in the absence of a netforce?

Yes

Can an object's velocity change direction when its acceleration is constant

Yes, this is possible, and a rock thrown straight up is an example

The x-component of a particle's velocity is sampled every 0.5 s. The data are fit with a straight line as shown in the v versus t plot. Assuming the fit is a good approximation to the motion, which of the force versus time plots best represents the x-component of the net force on the particle as a function of time?

b

In einstein's famous equation E=mc2, describe the relationship between matter and energy. E stands for energy, m stands for mass, and c is the speed of light in a vacuum. What are the si units for E?

kg times m^2/s^2

When subtracting several quantities

the quantities must all have the exact same units

Newton's 3rd law is also called the law of action and reaction. The "reaction" force does not cancel the "action" force because

they act on different bodies . The action and reaction forces are equal and in opposite directions.