Physics Multiple Choice Problems

If the acceleration of an object is negative, the object must be slowing down: T/F?

False This depends on the frame of reference. If it is moving in the negative direction, it could be speeding up in the negative direction.

0.0001776 can also be expressed as: a) 1.776 x 10^-3 b) 1.776 x 10^-4 c) 17.72 x 10^4 d) 1772 x 10^5 e) 177.2 x 10^7

b) 1.776 x 10^-4 0.0001776 Move the decimal to the right four places.

Express Pi (3.14159...) to four significant figures. (a) 3.142 (b) 3.141 (c) 3.1415 (d) 3.1414

(a) 3.141 1) ALL non-zero numbers (1,2,3,4,5,6,7,8,9) are ALWAYS significant. 2) ALL zeroes between non-zero numbers are ALWAYS significant. 3) ALL zeroes which are SIMULTANEOUSLY to the right of the decimal point AND at the end of the number are ALWAYS significant. 4) ALL zeroes which are to the left of a written decimal point and are in a number >= 10 are ALWAYS significant.

Suppose the force of the air drag on an object is proportional to the speed-squared of the object and in the direction opposite the objects velocity. If you throw an object upward, the magnitude of its acceleration is greatest: (a) at the top of its trajectory (b) right after the object is released (c) the acceleration is the same throughout

(b) right after the object is released Consider 3 stages of the trajectory: Just after release - acceleration = gravity + air resistance Top of trajectory - acceleration = gravity Just before caught - acceleration = gravity - air resistance

When can we be certain that the average velocity of an object is always equal to its instantaneous velocity? (a) always (b) never (c) only when the velocity is constant (d) only when the acceleration is changing at a constant rate

(c) only when the velocity is constant In other situations, the instantaneous velocity could be extremely high or, so long as there is then an extreme low to balance out the average. For this reason, we can only say instant = average if we know the velocity is unchanging.

If a flower is 6.5 cm wide, its width expressed in millimiters is ____ mm. a. Less than 6.5 b. Greater than 6.5

B. Greater than 6.5 If going from a large unit to a smaller unit, you must multiply the number.

You are standing on a skateboard, initially at rest. A ball is thrown at you. If you want to MINIMIZE your speed on the skateboard, should you catch or deflect the ball?

Catch Momentum will increase as delta v of the ball increases. Catching it minimizes delta v of the ball.

A small glider is coasting horizontally when it drops a piece of cargo from the bottom of the plane. Just after the cargo falls out, does the plane or the cargo speed up or slow down?

Neither change speed in the horizontal direction, as the horizontal forces have not changed (there are none) therefor there is no acceleration.

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

True If the line is horizontal, then the velocity is constant, therefore acceleration is 0.

When adding two numbers, the number of significant figures in the sum is equal to the number of significant figures in the least accurate of the numbers being added. True or False?

True If you have 2.0 + 2.05, you can only assume that your addition is as accurate as the less accurate number. 2.0 + 2.05 is 4.04, but the 2.0 could be 2.01, 2.04, etc. So we only know it is as close as 4.0

A stalled car is being pushed up a hill at a constant velocity by three people. The net force on the car is... a) Zero b) Up the hill and equal to the weight c) Down the hill and equal to the weight d) Down the hill and greater than the weight

Zero If there is a constant velocity, then acceleration is zero. If acceleration is zero, net force is zero.

Stannis baratheon is straining to life a large crate, without success because it is too heavy. We denote forces on the crate as follows: S is upward force of Stannis on the crate, N is the vertical contact force exerted on the crate by the force, and W is the weight of the crate. How are the magnitudes of thes forces related while stannis is being a bitch? a) S+N = W b) S + N <W c) S+N>W d) S=N

a) S+N = W if the crate isnt accellerating, then the net force must be zero. S is up, N is up, W is down.

While an object is in projectile motion (with upward being positive) with no air resistance a) The horizontal component of its velocity remains constant and the horizontal component of its acceleration is equal to -g b) The horizontal competent of its velocity remains constant and the vertical component of the acceleration is -g c) The horizontal component of its velocity remains constant and the vertical component of its acceleration is equal to zero d) the vertical component of both tees velocity and acceleration remain constant

b) The horizontal competent of its velocity remains constant and the vertical component of the acceleration is -g There is no outside forces to cause acceleration in the horizontal direction, so the horizontal velocity is constant. Gravity causes acceleration on the vertical component, and it is equal to -g

For general projectile motion, when the projectile is at the highest point of its trajectory, a) It's acceleration is zero b) Velocity is perpendicular to acceleration c) velocity and acceleration are both zero d) the horizontal component of its velocity is zero e) the horizontal and vertical components of velocity are zero

b) Velocity is perpendicular to acceleration The object has zero vertical velocity at the highest point, but still has negative acceleration in the DOWNWARD direciton. There is no outside forces to cause acceleration in the horizontal direction, so the velocity is constant but HORIZONTAL.

Suppose an object is moving with constant nonzero acceleration. Which of the following is an accurate statement concerning its motion? a) in equal times its speed changes by equal amounts b) in equal times its velocity changes by equal amounts c) in equal times it moves equal distances d) a graph of its position as a function of time has a constant slope e) a graph of its velocity as a function of time is a horizontal line

b) in equal times its velocity changes by equal amounts The velocity changes by equal amounts but the speed might not, for example if it crosses zero.

In order to lift a bucket of concrete, you must: a) pull harder on the bucket than it pulls on you b) pull at the same force the bucket pulls on you c) get in the bucket

b) pull at the same force the bucket pulls on you these are 3rd law pairs *****

Is it possible for a system to have negative potential energy? a) Yes, as long as kinetic energy is positive b) Yes, as long as the total energy is positive c) Yes, since the choice of the zero potential energy is arbitry d) No because this would have no physical meaning

c) Yes, since the choice of the zero potential energy is arbitry PE zero point is arbitrarily picked when you choose the frame of reference

You are seated in a bus and notice that a hand strap that is hanging from the ceiling hangs away from the vertical in the backward direction. From this observation you can conclude that: a) the velocity of the bus is forward b) the velocity of the bus is backward c) you can't conclude shit about velocity

c) you can't conclude shit about velocity If its hanging backwards the bus could either be stopping from a start, breaking in reverse, or just mid backflip-1080 off a swag xx420noscopexx jump

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: a) the force of gravity b) the normal force due to your contact with the floor of the bus c) the force due to static friction between you and the floor of the bus e) No forces were acting on you

e) No forces were acting on you The bus is accelerating - but you are not. You do not accelerate so there is no outside force.

Consider what happens when you jump in the air. Which of the following is the most accurate statement? a) you are able to spring up because the earth exerts a force upward on you that is greater than the downward force you exert on the earth b) When you jump up the earth exerts a force on you and you exert a greater force on the earth. c) it is the upward force exerted by the ground that pushes you up, but this force cannot exceed your weight d) since the ground is stationary, it cannot exert and upward force. Instead it is the internal forces of your muscles acting on your body. e) 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.

e) 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. Force of foot on earth equal and opposite to earth on foot, a third law pair.