Physics 1 Midterm

Answer 79 assuming a small amount of friction A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom if we ignore friction A - h1 B - h1 C - h2 D - h2 E - C and D equally

C

When the speed of your car is doubled, by what factor does its kinetic energy increase? A) sqrt2 B) 2 C) 4 D) 8

C) 4

How long would it take a car, starting from rest and accelerating uniformly in a straight line at 5 m/s^2, to cover a distance of 200 m? A) 9 s B) 10.5 s C) 12 s D) 15.5 s

A) 9 s

A baseball player hits a ball that soars high into the air. After the ball has left the bat, and while it is traveling upward, what is the direction of acceleration? Ignore air resistance.

Straight down.

If you push with force F on either the heavy box (m1) or the light box (m2), in which of the two cases below is the contact force between the two boxes larger A) Case A (small first) B) Case B (larger first) C) Same in both cases

A) Case A (small first)

Three blocks of mass 3m, 2m, and m are connected by strings and pulled with constant acceleration a. What is the relationship between the tension in each of the strings? (order 3m -t3- 2m -t2- m -t1- >>>) A) T1 > T2 > T3 B) T1 < T2 < T3 C) T1 = T2 = T3 D) all tensions 0 E) all tensions random

A) T1 > T2 > T3

A ball is thrown straight up. Neglecting air resistance, which statement is not true regarding the energy of the ball? A) The potential energy decreases while the ball is going up. B) The kinetic energy decreases while the ball is going up. C) The sum of the kinetic energy and potential energy is constant. D) The potential energy decreases when the ball is coming down. E) The kinetic energy increases when the ball is coming down.

A) The potential energy decreases while the ball is going up.

You and your dog go for a walk to the park. On the way, your dog takes many side trips to chase squirrels or examine fire hydrants. When you arrive at the park, do you and your dog have the same displacement? A) Yes B) No

A) Yes

A bullet fired from a rifle begins to fall A) as soon as it leaves the barrel B) after air friction reduces its speed C) not at all if air resistance is ignored

A) as soon as it leaves the barrel

A car travels along the x axis with increasing speed. We don't know if to the left or the right. Which of the graphs in the figure most closely represents the motion of the car? A) concave down, negative slope B) constant ROC, negative slope C) concave up, negative slope D) concave down, positive slope E) constant ROC, positive slope

A) concave down, negative slope

You push a heavy crate down a ramp at a constant velocity. Only four forces act on the crate. Which force does the greatest magnitude of work on the crate? A) force of friction B) force of gravity C) normal force D) force of you pushing E) net force

A) force of friction

To pull an old stump out of the ground, you and a friend tie two ropes to the stump. You pull on it with a force of 500 N to the north while your friend pulls with a force of 450 N to the northwest. The total force from the two ropes is A) less than 950 N B) more than 950 N C) exactly 950 N

A) less than 950 N

A truck is travelling horizontally to the right. When the truck starts to slow down, the crate on the (frictionless) truck bed starts to slide. IN what direction could the net force be on the crate? A) no direction. the net force is zero B) straight down (gravity) C) straight up (normal force) D) Horizontal and to the right E) Horizontal and to the left

A) no direction. the net force is zero

You are trying to hit a friend with a water balloon. He is sitting in the window of his dorm room directly above your position and is aiming at you with his water balloon! You aim straight at him and shoot and he does the same in the same instant. Do the water balloons hit each other? A) yes, they hit B) maybe -- depends on the speeds of the shots C) the shots are impossible D) no, they miss E) not really sure

A) yes, they hit

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? A)Both increase at the same rate. B)The velocity of the first rock increases faster than the velocity of the second. C)The velocity of the second rock increases faster than the velocity of the first. D)Both velocities stay constant.

A)Both increase at the same rate.

You are trying to push your stalled car. Although you apply a horizontal force of 400N to the car, it doesn't budge, and neither do you. What force(s) must also have a magnitude of 400N? A) The force exerted by the car on you B) The friction force exerted by the car on the road C) The normal force exerted by the road on you. D) The friction force exerted by the road on you

A,B,D

You throw a ball upward with an initial speed of 10 m/s. Assuming that there is no air resistance, what is its speed when it returns to you? A) more than 10 m/s B) 10 m/s C) less than 10 m/s D) zero E) Need more information

B) 10 m/s

A 50-N crate sits on a horizontal floor where the coefficient of static friction between the crate and the floor is 0.50. A 20-N force is applied to the crate acting to the right. What is the resulting static friction force acting on the crate? A) 20 N to the right. B) 20 N to the left. C) 25 N to the left. D) 25 N to the right. E) None of the above; the crate starts to move.

B) 20 N to the left.

From rest, we step on the gas of our Ferrari, providing a force F for 4 secs. During this time, the car moves 50 m. If the same force would be applied for 8 secs, how much would the car have traveled during this time? A) 250 m B) 200 m C) 150 m D) 100 m E) 50 m

B) 200 m

A car accelerates from rest to 30 km/h. Later, on a highway it accelerates from 30 km/h to 60 km/h. Which takes more energy, going from 0 to 30, or from 30 to 60? A) 0 to 30 km/h B) 30 to 60 km/h C) Both are the same

B) 30 to 60 km/h

From rest, we step on the gas of our Ferrari, providing a force F for 4 secs, speeding it up to a final speed v. If the applied force were only 1/2 F, how long would it have to be applied to reach the same final speed? A) 16 s B) 8 s C) 4 s D) 2 s E) 1 s

B) 8 s

If the rockets of a spaceship in outer space suddenly lose power and go off, the spaceship will gradually slow to a stop A) True B) False

B) False

In a collision between a huge SUV and a small hybrid car, the SUV exerts a larger force on the hybrid than the hybrid exerts on the SUV. A) True B) False C) It depends on whether the collision is a head-on collision or a rear-end collision

B) False

Now the cart is being pulled along a horizontal track by an external force and acceleration. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) It depends upon how much the track is tilted B) It falls behind the cart C) It falls in front of the cart D) It falls right back into the cart E) It remains at rest

B) It falls behind the cart

The acceleration due to gravity is lower on the Moon than on Earth. Which one of the following statements is true about the mass and weight of an astronaut on the Moon's surface, compared to Earth? A) Mass is less, weight is the same. B) Mass is the same, weight is less. C) Both mass and weight are less. D) Both mass and weight are the same.

B) Mass is the same, weight is less.

If the average velocity is non-zero over some time interval, does this mean that the instantaneous velocity is never zero during the same interval? A) Yes B) No C) It depends

B) No

If the position of a car is zero, does its speed have to be zero? A) Yes B) No C) It depends on the position

B) No

You drop a package from a plane flying at constant speed in a straight line. Without air resistance, the package will: A) Quickly lag behind the plane while falling B) Remain vertically under the plane while falling C) Move ahead of the plane while falling D) Not fall at all

B) Remain vertically under the plane while falling

A hunter is aiming horizontally at a monkey who is sitting in a tree. The monkey is so terrified when it sees the gun that it falls off the tree. At that very instant, the hunter pulls the trigger. What will happen? A) The bullet will miss the monkey because the monkey falls down while the bullet speeds straightforward. B) The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity. C) The bullet will miss the monkey because although both the monkey and the bullet are falling downward due to gravity, the monkey is falling faster. D) It depends on how far the hunter is from the monkey.

B) The bullet will hit the monkey because both the monkey and the bullet are falling downward at the same rate due to gravity.

One ball is dropped vertically from a window. At the same instant, a second ball is thrown horizontally from the same window. Which ball has the greater speed at ground level? A) The dropped ball B) The thrown ball C) Neither - they both have the same speed on impact D) It depends on how hard the ball was thrown

B) The thrown ball

A projectile is launched from the ground at an angle of 30 degrees. at what point in its trajectory does this projectile have the least speed? A) just after it is launched B) at the highest point in its flight C) just before it hits the ground D) halfway between the ground and the highest point E) speed is always constant

B) at the highest point in its flight

Two balls are thrown off a building with the same speed, one straight up and one at a 45 deg angle. Which statement is true if air resistance can be ignored? A) both hit the ground at the same time B) both hit the ground with the same speed C) the one thrown at an angle hits the ground with a lower speed D) the one thrown at an angle hits the ground with a higher speed E) both A and B

B) both hit the ground with the same speed

A person who normally weighs 700 N is riding in an elevator that is moving upward but slowing down at a steady rate. If this person is standing on a bathroom scale inside the elevator, what would the scale read? A) more than 700 N B) less than 700 N C) 700 N

B) less than 700 N

You push very hard on a heavy desk, trying to move it. You do work on the desk: A) whether or not it moves, as long as you are exerting a force. B) only if it starts moving C) only if it doesn't move D) never -- it does work on you E) None of the above

B) only if it starts moving

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 A) speeding up B) slowing down C) changing direction D) speeding up and changing direction E) slowing down and changing direction

B) slowing down

In the previous problem, which ball has the greater velocity at ground level? A) the "dropped" ball B) the "fired" ball C) neither--they both have the same velocity on impact D) it depends on how hard the ball was thrown

B) the "fired" ball

A golf ball is hit with a golf club. While the ball flies through the air, which forces act on the ball? Neglect air resistance. A) The force of the golf club acting on the ball B) the force of gravity acting on the ball C) the force of the ball moving forward through the air D) All of the above E) Both A and C

B) the force of gravity acting on the ball

Alice and Bill are at the top of a cliff of height H. Both throw a ball with initial speed v0, Alice straight down and Bill straight up. The speeds of the balls when they hit the ground are vA and vB. If there is no air resistance, which is true? A) vA < vB B) vA = vB C) vA > VB D) impossible to tell

B) vA = vB

The normal force on an extreme skier descending a very steep slope can be zero if A) his speed is great enough B) he leaves the slope (no longer touches the snow) C) the slope is greater than 75 degrees D) the slope is vertical (90 deg)

B,D

Which statements are not valid for a projectile? Take up as positive. Check all that apply. A) The projectile has the same x velocity at any point on its path. B) The acceleration of the projectile is positive and decreasing when the projectile is moving upwards, zero at the top, and increasingly negative as the projectile descends. C) The acceleration of the projectile is a constant negative value. D) The y component of the velocity of the projectile is zero at the highest point of the projectile's path. E) The velocity at the highest point is zero.

B,E

The spring-loaded gun can launch projectiles at different angles with the same launch speed. At what angle should the projectile be launched in order to travel the greatest distance before landing? A) 15 degrees B) 30 deg C) 45 deg D) 60 deg E) 75 deg

C) 45 deg

A person who normally weighs 700 N is riding in a rather swift elevator that is moving at a constant speed of 9.8 m/s. If this person is standing on a bathroom scale inside the elevator, what would the scale read? A) more than 700 N B) less than 700 C) 700 N

C) 700 N

You are riding in an enclosed train car moving at 90 km/h. If you throw a baseball straight up, where will the baseball land? A) In front of you. B) Behind you C) In your hand D) Can't decide from the given information

C) In your hand

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? A) More than 40 km/h B) Equal to 40 km/h C) Less than 40 km/h D) Not enough information

C) Less than 40 km/h

Alice and Bill are at the top of a building. Alice throws her ball downward. Bill simply drops his ball. Which ball has the greater acceleration just after release? A) Alice's Ball B) It depends on how hard the ball was thrown C) Neither--they both have the same acceleration D) Bill's ball

C) Neither--they both have the same acceleration

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?

C) Tension on the cord is constant, weight varies because mg

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

C) The acceleration of both balls is the same

What causes the boat to move forward? A) The force the paddle exerts on the water. B) The force the man exerts on the paddle. C) The force the water exerts on the paddle. D) The motion of the water itself.

C) The force the water exerts on the paddle.

Suppose an object is accelerated by a force of 100 N. Suddenly a second force of 100 N in the opposite direction is exerted on the object, so that the forces cancel. The object A) is brought to rest rapidly B) decelerated gradually to rest C) continues at the velocity it had before the second force was applied D) is brought to rest and then accelerates in the direction of the second force

C) continues at the velocity it had before the second force was applied

A person stands on a scale in an elevator. His apparent weight will be the greatest when the elevator A) is standing still B) is moving upward at constant velocity C) is accelerating upward D) is moving downward at constant velocity E) is accelerating downward

C) is accelerating upward

A man pushes a block up an incline at a constant speed. As the block moves up the incline. A) its kinetic energy and potential energy both increase B) its kinetic energy increases and its potential energy remains the same C) its potential energy increases and its kinetic energy remains the same D) its potential energy increases and its kinetic energy decreases by the same amount

C) its potential energy increases and its kinetic energy remains the same

When a skier skis down a hill, the normal force exerted on the skier by the hill is A) equal to the weight of the skier B) greater than the weight of the skier C) less than the weight of the skier

C) less than the weight of the skier

A bowling ball is dropped from a height h onto the center of a trampoline, which launches the ball back up into the air. How high will the ball rise? A) significantly less than h B) more than h. the exact amount depends on the mass of the ball and the springiness of the trampoline C) no more than h -- probably a little less D) cannot tell without knowing the characteristics of the trampoline

C) no more than h -- probably a little less

A baseball is hit high and far. Which of the following statements is true? At the highest point, A) the magnitude of the acceleration is zero B) the magnitude of the velocity is zero C) the magnitude of the velocity is the slowest D) more than one of the above is true E) none of the above are true

C) the magnitude of the velocity is the slowest

If you pound a feather with a hammer, which one feels a greater force? A) always the feather B) always the hammer C) the size of the force is always exactly the same on both of them D) If the feather moves, then it felt the greater force. Otherwise the force was the same on both

C) the size of the force is always exactly the same on both of them

From the same height (and at the same time), one ball is dropped and another ball is fired horizontally. Which one will hit the ground first? A) the "dropped" ball B) the "fired" ball C) they both hit at the same time D) it depends on how hard the ball was fired E) it depends on the initial height

C) they both hit at the same time

A ball is thrown straight up. What are the velocity and acceleration of the ball at the highest point in its path? A) v=0, a=0 B) v=0, a= 9.8 m/s^2 up C) v=0, a= 9.8 m/s^2 down D) v=9.8 m/s up, a=0 E) v=9.8 m/s down, a=0

C) v=0, a= 9.8 m/s^2 down

When throwing a ball straight up, which of the following is true about its velocity v and its acceleration a at the highest point in its path? A) both v=0 and a=0 B) v≠0, but a=0 C) v=0, but a≠0 D) both v≠0 and a≠0 E) not really sure

C) v=0, but a≠0

In which of the following cases does a car have a negative velocity and a positive acceleration? A car that is traveling in the A) -x direction at a constant 20 m/s B) -x direction increasing in speed C) +x direction increasing in speed D) -x direction decreasing in speed E) +x direction decreasing in speed

D) -x direction decreasing in speed

A force F acts on mass M for a time interval T, giving it a final speed v. If the same force acts for the same time on a different mass 2M, what would be the final speed of the bigger mass? A) 4 v B) 2 v C) v D) 1/2 v E) 1/4 v

D) 1/2 v

Two blocks of masses 2m and m are in contact on a horizontal frictionless surface. If a force F is applied to mass 2m, what is the force on mass m? A) 2 F B) F C) 1/2 F D) 1/3 F E) 1/4 F

D) 1/3 F

A car travelling at a velocity v can stop in a minimum distance d. What would be the car's minimum stopping distance if it were traveling at a velocity of 2v? A) d B) sqrt2 d C) 2d D) 4d E) 8d

D) 4d

A small cart is rolling at constant velocity on a flat track. It fires a ball straight up into the air as it moves. After it is fired, what happens to the ball? A) It depends on how fast the cart is moving B) It falls behind the cart C) It falls in front of the cart D) It falls right back into the cart E) It remains at rest

D) It falls right back into the cart

The same small cart is now rolling down an inclined track and accelerating. It fires a ball straight out of the cannon as it moves. After it is fired, what happens to the ball? A) It depends upon how much the track is tilted B) It falls behind the cart C) It falls in front of the bart D) It falls right back into the cart E) It remains at rest

D) It falls right back into the cart

An object is moving with constant non-zero velocity. Which of the following statements about it must be true? A) A constant force is being applied to it in the direction of motion B) A constant force is being applied to it in the direction opposite of motion C) A constant force is being applied to it perpendicular to the direction of motion D) The net force on the object is zero E) Its acceleration is in the same direction as its velocity

D) The net force on the object is zero

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. Which statement is true? A)The object will slow down, eventually coming to a complete stop. B)The object cannot have a negative acceleration and be moving to the right C)The object will continue to move to the right, slowing down but never coming to a complete stop D)The object will slow down, momentarily stopping, then pick up speed moving to the left

D) The object will slow down, momentarily stopping, then pick up speed moving to the left

You are standing in a moving bus, facing forward, when you suddenly slide forward as the bus comes to an immediate stop. What force caused you to slide forward? A) gravity B) the normal force due to your contact with the floor of the bus C) the force due to friction between you and the floor of the bus D) There is not a force causing you to slide forward

D) There is not a force causing you to slide forward

A push of magnitude P acts on a box of weight W as shown in the figure. The push is directed at an angle ? 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 A) W. B) W + P. C) W + P cos θ. D) W + P sin θ. E) W - P sin θ.

D) W + P sin θ.

Which of the three kicks is in the air for the longest time? They all reach the same maximum height h. Ignore air resistance A) short B) medium C) long D) all the same time

D) all the same time

A 75-N box rests on a perfectly smooth horizontal surface. The minimum force need to start the box moving is A) 75 N B) 7.5 N C) 750 N D) any horizontal force greater than zero

D) any horizontal force greater than zero

A box sits on a flat board. You lift one end of the board, making an angle with the floor. As you increase the angle, the box will eventually begin to slide down. Why? A) component of the gravity force parallel to the plane increased B) coeff. static friction decreased C) normal force exerted by teh board decreased D) both A and C E) all of a, b, and c

D) both A and C

A bear sling is used in some national parks for placing backpackers' food out of the reach of bears. As the backpacker raises the pack by pulling down on the rope, the force F needed: A) decreases as the pack rises until the rope is straight across B) doesn't change C) increases until the rope is straight D) increases but the rope always sags where the pack hangs

D) increases but the rope always sags where the pack hangs

You are pushing a heavy box across a rough floor. When you are initially pushing the box and it is accelerating A) you exert a force on the box, but the box does not exert a force on you B) the box is so heavy it exerts a force on you, but you do not exert a force on the box C) the force you exert on the box is greater than the force of the box pushing back on you D) the force you exert on the box is equal to the force of the box pushing back on you E) the force that the box exerts on you is greater than the force you exert on the box

D) the force you exert on the box is equal to the force of the box pushing back on you

Matt, in the foreground, is able to move the large truck because A) he is stronger than the truck B) he is heavier in some respects than the truck C) he exerts a greater force on the truck than the truck exerts back on him D) the ground exerts a greater friction force on Matt than it does on the truck E) the truck offers no resistance because its brakes are off

D) the ground exerts a greater friction force on Matt than it does on the truck

Engines, including car engines, are rated in horsepower. What is horsepower? A) The force needed to start the engine B) the force needed to keep the engine running at a steady rate C) the energy the engine needs to obtain from gasoline or some other source D) the rate at which the engine can do work E) the amount of work the engine can perform

D) the rate at which the engine can do work

A force F acts on mass m1 giving acceleration a1. The same force acts on a different mass m2 giving acceleration a2 = 2a1. If m1 and m2 are glued together and the same force F acts on this combination, what is the resulting acceleration? A) 3/4 a1 B) 3/2 a1 C) 1/2 a1 D) 4/3 a1 E) 2/3 a1

E) 2/3 a1

A skier starts from rest at the top of each of the hills shown in the figure. On which hill will the skier have the highest speed at the bottom if we ignore friction A - h1 B - h1 C - h2 D - h2 E - C and D equally

E) C and D equally

Three boxes are pulled along a horizontal frictionless floor by a constant horizontal pull P. The boxes are connected by very light horizontal strings having tensions T1 and T2 as shown in the figure. Which of the following statements about the tensions is correct? (There could be more than one correct choice.) A) T1 = P B) T2 = P C) T1 + T2 = P D) T2 > T1 E) T1 > T2

E) T1 > T2

In which case does block m experience a larger acceleration? In (1) there is a 10 kg mass hanging from a rope and falling. In (2) a hand is providing a constant downward force of 98 N. Assume massless ropes. A) case 1 B) acceleration is zero C) both cases are the same D) depends on the value of m E) case 2

E) case 2

A ball is thrown straight up. At what point does the ball have the most energy? Ignore air resistance A) at the highest point of its path B) when it is first thrown C) just before it hits the ground D) when the ball is halfway to the highest point of its path E) everywhere; the energy of the ball is the same at all of these points

E) everywhere; the energy of the ball is the same at all of these points

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? A) right 100N B) right and left both 100N C) two right 100N D) right 50 N E) no horizontal forces act on A

E) no horizontal forces act on A

A box of weight 100 N is at rest on a floor where μs = 0.5. A rope is attached to the box and pulled horizontally with tension T = 30 N. Which way does the box move? A) moves to the left B) moves to the right C) moves up D) moves down E) the box does not move

E) the box does not move