Physics Quizzes Combined S1

If the velocity versus time graph of an object is a straight line making an angle of +30° (counter clockwise) with the time axis, the object is

moving with constant non-zero acceleration.

You are in a train traveling on a horizontal track and notice that a piece of luggage starts to slide directly toward the front of the train. From this observation, you can conclude that this train is

slowing down.

The reason an astronaut in an Earth satellite feels weightless is that

the astronaut is in the state of free fall.

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

when the velocity is constant

At t = 0, an object is 10 m above the ground, moving upward with a velocity of 1 m/s. Which of the following equations correctly describes the object's position as a function of time given a coordinate axis where y = 0 at the ground and +y is downward?

y = (-10 m) + (-1 m/s)t + (1/2)(9.8 m/s2)t2

An object has an initial velocity of -4 m/sand a constant acceleration of 3 m/s2.What is its velocity at t = 2 s?

+2 m/s

What is the displacement (x - x0) between t = 0 s and t = 2 s given that the equation for position as a function of time is x = 3t + 0(x in meters, t in seconds)?

+6 m

What is the displacement of "you" between t = 0 and t = 2 s?

+6 m

A boy throws a rock with an initial velocity of 3.13 m/s at 30.0° above the horizontal. How long does it take for the rock to reach the maximum height of its trajectory if effects of air are negligibly small and g = 9.80 m/s2?

0.160 s

An object slides on a level floor. It slows and comes to a stop with a constant acceleration of magnitude 2.4 m/s2. What is the coefficient of kinetic friction between the object and the floor?

0.24

A car is traveling north at After 12 s its velocity is in the same direction. Find the magnitude and direction of the car's average acceleration.

0.30 m/s2, south

An object starts at rest 3 m from the origin and has an acceleration of -1 m/s2. What is its position at t = 2 s?

1 m

Two forces are exerted on a 55-kg object. One force has magnitude 65 N directed 59° clockwise from the positive x-axis, and the other has a magnitude 35 N at 32° clockwise from the positive y-axis. Assuming no other forces, what is the magnitude of this object's acceleration?

1.1 m/s2

The free-fall acceleration on Planet A is one-sixth what it is on Planet B, and the radius of the Planet A is one-fourth that of Planet B. The mass of Planet A is what fraction of the mass of Planet B?

1/96

A ball is thrown with an initial velocity of 20 m/s at an angle of 60° above the horizontal. If we can neglect air, what is the horizontal component of its instantaneous velocity at the exact top of its trajectory?

10 m/s

Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the lower block, B?

100N <--- B ---> 100N

At t = 0, an object is 30 m above the ground,moving upward with a velocity of 1 m/s.Where is the object at t = 2 s(approximate g of 10 m/s2)?

12 m

Sammy went hiking between two camps that were separated by about 10 kilometers (km). He hiked approximately 16 km to get from one camp to the other. Which of the following is the CORRECT translation of 10 km and 16 km into the language of physical quantities?

16 km is the path length; 10 km is the distance.

A fisherman casts his bait toward the river at an angle of 25° above the horizontal. As the line unravels, he notices that the bait and hook reach a maximum height of 2.9 m. What was the initial velocity he launched the bait with? Assume that the line exerts no appreciable drag force on the bait and hook and that the effects of air are negligible.

18 m/s

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

186,000 mi and 40 km southwest

Acceleration is sometimes expressed in multiples of g, where is the acceleration of an object due to the earth's gravity. In a car crash, the car's forward velocity may go from to in How many g's are experienced, on average, by the driver?

20 g

A hockey puck slides off the edge of a platform with an initial velocity of 20 m/s horizontally. The height of the platform above the ground is 2.0 m. What is the magnitude of the velocity of the puck just before it touches the ground? You can neglect air.

21 m/s

As shown in the figure, a projectile is fired at time t = 0.00 s, from point 0 at the upper edge of a cliff, with initial velocity components of v0x = 30 m/s and v0y = 300 m/s.The projectile rises and then falls into the sea at point P. The time of flight of the projectile is 75.0 s, and air effects are negligible. At this location, g = 9.80 m/s2. What is the horizontal distance D?

2250 m

An object moves 15.0 m north and then 11.0 m south. Find both the distance it has traveled and the magnitude of its displacement.

26.0 m, 4.0 m

Starting from rest, a dragster travels a straight 1/4 mi racetrack in 6.70 s with constant acceleration. What is its velocity when it crosses the finish line?

269 mi/h

An airplane travels at 300 mi/h south for 2.00 h and then at 250 mi/h north for 750 miles. What is the average speed for the trip?

270 mi/h

A 6.0-kg box slides down an inclined plane that makes an angle of 39° with the horizontal. If the coefficient of kinetic friction is 0.40, at what rate does the box accelerate down the slope?

3.1 m/s2

A boy kicks a football from ground level with an initial velocity of 20 m/s at an angle of 30° above the horizontal. What is the horizontal distance to the point where the football hits the ground if we neglect air?

35 m

Jason takes off across level water on his jet-powered skis. The combined mass of Jason and his skis is 75 kg (the mass of the fuel is negligible). Water exerts a force of 200 N on the skis. The coefficient of kinetic friction between the skis and water is 0.10. Unfortunately, the skis run out of fuel after only 41 s. How far from his starting point has Jason traveled when he finally coasts to a stop?

3900 m

A 15-kg block is on a frictionless ramp that is inclined at 20° above the horizontal. It is connected by a very light string over an ideal pulley at the top edge of the ramp to a hanging 19-kg block, as shown in the figure. The string pulls on the 15-kg block parallel to the surface of the ramp. Find the magnitude of the acceleration of the 19-kg block after the system is gently released.

4.0 m/s2

A train starts from rest and accelerates uniformly until it has traveled 2.1 km and acquired a forward velocity of The train then moves at a constant velocity of for 400 s. The train then slows down uniformly at until it is brought to a halt. The distance traveled by the train while slowing down is closest to

4.4 km

When Jeff ran up a hill at 7.0 m/s, the horizontal component of his velocity vector was 5.1 m/s. What was the vertical component of Jeff's velocity?

4.8 m/s

Two planets have the same free-fall acceleration on the surface, but planet B has twice the radius of planet A. If planet A has mass m, what is the mass of planet B?

4m

A runner runs around a track consisting of two parallel lines 96 m long connected at the ends by two semicircles with a radius of 49 m. She completes one lap in 100 seconds. What is her average speed?

5.0 m/s

A boy throws a ball with an initial velocity of 25 m/s at an angle of 30° above the horizontal. If you neglect air, how high above the projection point is the ball after 2.0 s?

5.4 m

A light-year is the distance that light travels in one year. The speed of light is 3.00 × 108 m/s. How many miles are there in one light-year? (1 mi = 1609 m, 1 y = 365 d)

5.88 × 10^12 mi

The figure shows a block of mass M hanging at rest. The light wire fastened to the wall is horizontal and exerts a tension force of 38 N on the block. The wire fastened to the ceiling is also very light, exerts a tension force of 59 N on the block, 59N, and makes an angle θ with the ceiling. Find the angle θ.

50°

A truck is using a hook to tow a car whose mass is one quarter that of the truck. If the force exerted by the truck on the car is 6000 N, then the force exerted by the car on the truck is

6000 N.

A ball thrown horizontally from a point 24 m above the ground, strikes the ground after traveling horizontally a distance of 18 m. With what speed was it thrown, assuming negligible air effects?

8.1 m/s

The coefficients of static and kinetic friction between a 3.0-kg box and a horizontal desktop are 0.40 and 0.30, respectively. What is the force of friction that the desktop exerts on the box when a 15-N horizontal push is exerted on the box?

8.8 N

When an object is thrown upward, what is its acceleration (given a coordinate axis choice where +y is downward)?

9.8 m/s2

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

90° to 180°

A stone is thrown horizontally with an initial speed of 10 m/s from the edge of a cliff. A stopwatch measures the stone's trajectory time from the top of the cliff to the bottom to be 4.3 s. What is the height of the cliff if effects of air are negligible?

91 m

Why is the following statement true? "Displacement is equal to the area between a velocity-versus-time graph line and the time axis with a positive or negative sign."

All of the above are true.

Which of the following situations is impossible?

An object has constant non-zero velocity and changing acceleration.

Which of the following situations corresponds to a positive acceleration?

An object moving in the -x direction and slowing down

The magnitude of is 5.5 m, and this vector lies in the second quadrant and makes an angle of 34° with the +y-axis. The components of are closest to

Ax = -3.1 m, Ay = 4.6 m.

Two objects of unequal masses, M and m (M > m), are connected by a very light cord passing over an ideal pulley of negligible mass. When released, the system accelerates, and friction is negligible. Which one of the following free-body diagrams most realistically represents the forces acting on the two objects in the moving system?

B - M: medium long on top and longer on bottom m: same as top on M but shorter on the bottom.

A racing car accelerates uniformly from rest along a straight track. This track has markers spaced at equal distances along it from the start, as shown in the figure. The car reaches a speed of 140 km/h as it passes marker 2. Where on the track was the car when it was traveling at half this speed, that is at 70 km/h?

Before marker 1

What can we conclude about the motion of car A compared to car B?

Car B is moving faster than car A.

A displacement vector is 34.0 m in length and is directed 60.0° east of north. Selecting from the choices in the table below, what are the components of this vector? Northward Eastward 1 29.4 m 17.0 m2 18.2 m 28.1 m3 22.4 m 11.5 m4 17.0 m 29.4 m5 25.2 m 18.2 m

Choice 4

Which of the following statements is true?

Distance is always the length of the displacement.

A satellite is in orbit around the earth. Which one feels the greater force?

Earth and the satellite feel exactly the same force.

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about normal force F on the block due to the ramp?

F = mg cos θ

A block of mass m sits at rest on a rough inclined ramp that makes an angle θ with the horizontal. What must be true about the force of static friction f exerted on the block?

F = mg sin θ

A box is placed on a table which rests on the floor. The box pushes on the table; the reaction force to the box's push on the table is the table's push on the floor.

False

If a vector's components are all negative, then the magnitude of the vector is negative.

False

If the velocity of an object is zero at some point, then its acceleration must also be zero at that point.

False

If you swing a bucket of water fast enough in a vertical circle, at the highest point the water does not spill out. This happens because an outward force balances the pull of Earth on the water.

False

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

False

The Moon is accelerated toward the earth, so it is gradually getting closer to the earth.

False

By drawing the graph from the motion diagram, what are we NOT able to do?

Infer the position of the object before the initial point in the motion diagram

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 positive.

A ball is thrown straight up, reaches a maximum height, then falls to its initial height. Which of the following statements about the direction of the velocity and acceleration of the ball as it is going up is correct?

Its velocity points upward and its acceleration points downward.

Two blocks, A and B, are being pulled to the right along a horizontal surface by a horizontal 100-N pull, as shown in the figure. Both of them are moving together at a constant velocity of 2.0 m/s to the right, and both weigh the same. Which of the figures below shows a correct free-body diagram of the horizontal forces acting on the upper block, A?

Just the box A. No horizontal forces act on A.

A child standing on a bridge throws a rock straight down. The rock leaves the child's hand at time t = 0 s. If we take upward as the positive direction, which of the graphs shown below best represents the velocity of the stone as a function of time?

Negative, linear, and starts below the origin on the y axis.

A crate is sliding down an inclined ramp at a constant speed of 0.55 m/s. The vector sum of all the forces acting on this crate must point

None of the above choices is correct.

Compare two objects (positions are in meters, time is in seconds):x1 = 5t + 3x2 = -4t + 0Which of the following is incorrect?

Object 2 has a velocity of 4 m/s.

As shown in the figure, a woman is straining to lift a large crate, but without success because it is too heavy. We denote the forces on the crate as follows: P is the magnitude of the upward force being exerted on the crate by the person, C is the magnitude of the vertical contact force on the crate by the floor, and W is the weight of the crate. How are the magnitudes of these forces related while the person is trying unsuccessfully to lift the crate?

P + C = W

Which parameter can we NOT determine from the following graph?

Position of the object at t = 8 s

The object represented by the following motion diagram is:

Slowing down.

Under what condition is average velocity equal to the average of the object's initial and final velocity?

The acceleration is constant.

Suppose that an object is moving with a constant velocity. Which statement concerning its acceleration must be correct?

The acceleration is equal to zero.

A car's motion with respect to the ground is described by the following function:x = (-48 m) + (+12 m/s)t + (-0.5 m/s2)t2Which statement is INCORRECT?

The acceleration of the car is -0.5 m/s2.

Given the following motion diagram, what is the direction of the change in the velocity vector?

The change in velocity vector is to the right.

A cyclist moves at a constant velocity of -8 m/s and starts at x0 = 0 m. Which of the following statements is incorrect?

The cyclist is at x = +8 m at t = 1 s.

What can we infer from the following graph?

The object gets farther from the origin with time.

If the velocity change vector points in the opposite direction as the velocity arrows, what can we conclude?

The object is slowing down steadily.

The following equation describes an object's motion: x = (2 m) + (0)t + (1/2)(-1 m/s2)t2Which of the following statements is correct?

The object is speeding up.

Satellite A has twice the mass of satellite B, and moves at the same orbital distance from Earth as satellite B. Compare the speeds of the two satellites.

The speed of B is equal to the speed of A.

A person starts at xi = -2.0 m and endsat xf = 3.0 m. Given the ground as a reference frame and a coordinate axis pointing to the right, which of the following is NOT FALSE ?

The value of the displacement dx is +5.0 m.

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.

They are traveling at the same speed.

Consider a deer that runs from point A to point B. The distance the deer runs can be greater than the magnitude of its displacement, but the magnitude of the displacement can never be greater than the distance it runs.

True

Which of the following statements is always true about the description of motion of an object by two observers?

Two observers using the same coordinate axis (including the origin) and reference frame will always have the same description of motion.

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle θ below the horizontal, and the box remains a rest. The box rests on a horizontal surface that has some friction with the box. The normal force on the box due to the floor is equal to

W + P sin θ

The equation for your position as a function of time is x = 3t + 0 (x in meters, t in seconds).Compare that to the graph of your velocity. Which statement is incorrect?

We can find your initial position from either the equation or the graph.

Which information about a moving object can we NOT extract from a motion diagram?

What the object was doing before the first dot of the motion diagram

An object is moving with constant non-zero acceleration in the +x direction. The position versus time graph of this object is

a parabolic curve.

If the non-zero velocity change vectors are all the same,what can we conclude?

a. The object is speeding up steadily. b. The object is slowing down steadily.

Which of the following statements is consistent with what the variables indicate for the general linear function y(x) = kx + b?

b is the y-intercept.

What can we conclude about the motion of the two objects represented by the following motion diagrams?

b. Both objects are moving at constant speed.

If the acceleration of an object is zero, then that object cannot be moving.

b. False

An object is moving with constant non-zero velocity in the +x direction. The position versus time graph of this object is

c. a straight line making an angle with the time axis.

A satellite encircles Mars at a distance above its surface equal to 3 times the radius of Mars. If gm is the free-fall acceleration at the surface of Mars, what is the free-fall acceleration at the location of the satellite?

gm/16

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

increases.

When a ball is thrown straight up with no air resistance, the acceleration at its highest point

is downward

An object moving in the +x direction experiences an acceleration of +2.0 m/s2. This means the object

is increasing its velocity by 2.0 m/s every second.

You drive 6.0 km at 50 km/h and then another 6.0 km at 90 km/h. Your average speed over the 12 km drive will be

less than 70 km/h.

Two boxes P and Q on a perfectly smooth horizontal surface are connected by a light horizontal cord. The mass of P is greater than that of Q. A horizontal force is applied to box Q as shown in the figure, accelerating the bodies to the right. The magnitude of the force exerted by the connecting cord on body P is

less than F but not zero.

What are the SI units of (1/2)axt2?

m