Physics Exam 1 (chapters 1-5)

A bird flies at 8 km/h in the sky. A car speeds at 8 km/h on the road. What is the speed of the bird relative to the car? A. 0 B. 8 km/h C. 16 km/h D. less than 8 km/h

0 * motion is relative The bird flies as fast as the car runs on the road. They are stationary relative to each other.

Two boys fighting over a wagon. Boy #1 is pulling to the right with a force of 55.0 N. Boy #2 is pulling to the left with a force of 35.0 N. The wagon's Net Force is: A. 55 N Right B. 35.0 N Left C. 20.0 N Left D. 0.0 N E. 20.0 N Right

20.0 N Right *Net Force = 55.0 N Right + 35 N left -> 55- 35 = 20 N Right Right is positive, left is negative. Right is a bigger #, therefore the answer goes with the larger # (55).

If a motor vehicle increases its speed by 20 m/s in 5 seconds, its acceleration is A. 4 m/s B. 4 m/s^2 C. 4 m D. 0

4 m/s^2 *a= v/t = 20/5 = 4 Acceleration unit is m/s^2

A rock is thrown straight up. When the rock reaches its MAXIMUM height, it has a Velocity of ____ and an Acceleration of ____ in the vertical direction. Define j as positive direction which is going up. A. 0 m/s 𝒋; -9.8 m/𝒔^2 𝒋 B. 0 m/s ȷ̂; 9.8 m/s2 ȷ̂ C. -9.8 m/s ȷ̂; 0 m/s2 ȷ̂ D. 9.8 m/s ȷ̂; 9.8 m/s2 ȷ̂

A. 0 m/s 𝒋; -9.8 m/𝒔𝟐 𝒋 * acceleration is always 9.8m/s2 going down due to gravity at maximum height, velocity is always zero

When a 10 kg block is simultaneously pushed eastward with 20N and westward 15 N, the acceleration of the block is A. 0.5 𝒎𝒎 𝒔𝒔𝟐𝟐 ⁄ east B. 0.5 𝑚𝑚 𝑠𝑠2 ⁄ west C. 0.5 𝑚𝑚 𝑠𝑠2 ⁄ east-west D. None of the above

A. 0.5 𝒎𝒎 𝒔𝒔𝟐𝟐 ⁄ east * a = F/m = 20-15/ 10 = 0.5 m/s^2 east

Pipe #1 has an area of 0.500 m2 while Pipe #2 has an area of 3.50 m2 . If the water's speed through Pipe #1 is 8.00 m/s, what is its speed through Pipe #2? The Equation of Continuity is: 𝐴1 × 𝑣1 = 𝐴2 × 𝑣2 A. 1.14 m/s B. 56.0 m/s C. 0.219 m/s D. 0.875 m/s

A. 1.14 m/s * 0.500 * 8.00 /3.50 = 1.14 m/s

A 100 kg vehicle accelerates at 1 m/s^2 when the net force on it is A. 100 N B. 10 N C. 1 N D. 1000 N

A. 100 N * a= F/m -> F= m * a = 100 *1 = 100N= N Newton's 2nd law

A 75.0-kg man climbs 4.50 meters up a ladder. The man's weight is 735 newtons. Calculate the man's Gravitational Potential Energy when he is 4.50 meters up the ladder. Assume the ground is Zero GPE. GPE is defined as: GPE = mass * g * height A. 3310 J B. 338 J C. 4000 J D. 32900 J

A. 3310 J * GPE = (75.0 kg) (9.8 m/s2) (4.50 m) = 3310 J * mass is in kg, weight is in N

Charlie stands with one foot on one bathroom scale and his other foot on a second bathroom scale. Each scale reads 350 N. What is Charlie's weight? A. 700 N B. 350 N C. 175 N D. Not enough information

A. 700 N * Charlie's at rest in the vertical direction. His acceleration and net force are both zero vertically. Consequently, all the forces have to add up to zero. Both scales are pushing upward on Charlie (for a total force of 700 N up.) which is countered by Charlie's weight (700 N down).

A 0.125-N ball falls into a river having a depth of 8.91 meters. The ball's mass is 0.0127 kg and its volume is 4.70 X 10 - 6 cubic meters. Calculate the fluid pressure {Pa} exerted on the ball. The formula for fluid pressure is: P= P(fluid) * g * h A. 87,300 Pa B. 1.11 Pa C. 0.0461 Pa D. 10,900 Pa

A. 87, 300 Pa * 1000 * 9.80 * 8.91 = 87,300

A satellite in orbit around Earth is above Earth's A. atmosphere B. gravitational field C. both of the above D. neither of the above.

A. atmosphere

A satellite in elliptical orbit about Earth travels fastest when it moves A. close to Earth; B. far from Earth; C. in either direction - the same everywhere; D. between the near and far points from Earth.

A. close to Earth * the closer the satellite is to Earth, the lower of gravitational potential energy, and the higher of the kinetic energy

A Falling object that reaches terminal velocity continues to have A. speed B. a nonzero net force C. acceleration D. all of the above.

A. speed * at terminal velocity, both net force and acceleration are zero.

The amount of air resistance on a 0.8 N flying squirrel for terminal speed is A. less than 0.8 N B. 0.8 N C. more than 0.8 N D. depends on the orientation of its body

B. 0.8 N * for terminal speed, the net force must be equal to zero, no matter what the orientation of the squirrel's body

A piece of clay moving with 1 unit of momentum strikes and sticks to a heavy bowling ball initially at rest. After the clay sticks, both ideally move with a combined momentum of A. less than 1 unit; B. 1 unit; C. more than 1 unit; D. no momentum at all.

B. 1 unit * when objects collide in the absence of external forces, net momentum is conserved, before = after

Two pistons are connected through a hydraulic system. Piston #2 has an area of 55.0 ft2 and supports a 1,200-pound crate. If Piston #1 supports a 200-pound weight, what area should Piston #1 have to keep the system in equilibrium? The hydraulic formula is: F1/ A1 = F2/ A2 A. 4360 ft^2 B. 9.17 ft^2 C. 330 ft^2 D. 0.167 ft^2

B. 9.17 ft^2

The difference between speed and velocity mostly involves: A. Amount B. Direction C. Acceleration D. All of the above

B. Direction *speed is the magnitude of velocity. Velocity is a vector which also involves direction.

An object has a mass of 35.0 kg and a weight of 343 N on Earth's surface. If the object was sent to the Moon, which quantity (mass, weight, or both) would remain unchanged? A. Weight would still be 343 N on the Moon as it is on Earth. B. Weight would still be 35.0 kg on the Moon as it is on Earth. C. Both. Mass and weight would be the same on the moon as they are on earth. D. Neither. Mass and weight would both be different on the Moon from what they are on Earth.

B. Weight would still be 35.0 kg on the Moon as it is on Earth. *Mass remains constant no matter the location.*

If gravity between the Sun and Earth suddenly vanished, Earth would move in A. a curved path B. a straight-line path C. an outward spiral D. an inward spiral

B. a straight-line path * without gravity from the Sun because of inertia, the Earth would keep its velocity.

When a car rounds a curve, which of the following statements must be true? A. moving uniformly B. accelerating C. in rotational equilibrium D. changing its speed

B. accelerating * velocity changes its direction when the car goes on a curve. There must be an acceleration making this happen.

Your friend says that impulse equals momentum. This statement isn't correct, and the missing word is A. acceleration B. change C. speed or velocity D. work

B. change * impulse = change in momentum

If the distance between two planets decreases to half, the force of gravity between them The force of gravity is defined as: 𝐹 = 𝐺 m1 ∗ m2 /𝑑2 A. doubles. B. quadruples. C. decreases to half. D. decreases to one quarter.

B. quadruples * d is reduced to d/2, then F = G m1 * m2 / (d/2)^2 = G m1 * m2 / d^2 *4

A ball rolls off the edge of a table and hits the floor below. If the ball's speed were somewhat greater, the time to hit the floor would be A. less. B. same. C. more. D. unknown.

B. same

The impulse-momentum relationship is a direct result of Newton's A. First law B. Second Law C. Third Law D. Law of Gravity

B. second law

According to the equation for gravity, if you travel far enough from Earth, the gravitational influence of Earth will A. reach 0; B. still be there; C. actually increase; D. none of the above.

B. still be there * The gravity equation: as d approaches infinity, F approaches zero, but never reaches zero

Without air resistance, the time for a vertically tossed ball to return to where it was thrown from is A. 10 m/s for every second in the air. B. the same as the time going upward. C. less than the time going upward. D. more than the time going upward.

B. the same as the time going upward. * throw-upward, then free-fall motion.

The force due to gravity on a body is the body's A. mass B. weight C. both D. neither

B. weight * weight is the amount of gravitational pull on an object

Which of the following equations best illustrates the usefulness of automobile air bags? A. 𝐹 = ma B. 𝑭∆𝒕 = 𝒎v C. 𝐾E = 1/2 𝑚𝑣2 D. 𝑃E = 𝑚gℎ

B. 𝑭∆𝒕 = 𝒎v * extend the time, decrease the force

A 1,350-N safe needs to be moved 5.00 meters to a new location in an office. The office manager exerts a horizontal force of 500. newtons, but he is unable to move the safe. Calculate the Work done by the manager on the safe. Work is defined as: Work = Force * Distance A. 2500 J B. 6750 J C. 0 J D. 67500 J

C. 0 J * if the safe does NOT move, then NO work has been done.

A 0.125-N ball falls into a vat of Olive Oil (930. kg/m3 ) to a depth of 2.71 meters. The ball's mass is 0.0127 kg and its volume is 4.70 * 10 - 6 cubic meters. Calculate the buoyancy force exerted on the ball. The formula for buoyancy force is: 𝐹b = P (fluid) * g * 𝑉(object) A. 5.46 × 10−6 N B. 0.0460 N C. 0.0428 N D. 0.00430 N

C. 0.0428 N * 930 * 9.80 * (4.70 x 10^-6) = 0.0428 N

A 1-kg iron ball and a 10-kg iron ball are dropped from rest from the top of a one-story building. When hitting the ground below, compared with the 1-kg ball, the 10-kg ball has A. less momentum and KE. B. same momentum and KE. C. 10 times as much momentum and 10 times as much KE. D. 10 times as much momentum and 100 times as much KE.

C. 10 times as much momentum and 10 times as much KE * both have equal speeds. both momentum and KE are directly proportional to mass

A 1-kg ball has twice as much speed as a 10-kg ball. Compared with the 1-kg ball, the 10-kg ball has A. 100 times as much momentum B. 10 times as much momentum C. 5 times as much momentum D. The same momentum

C. 5 times as much momentum * momentum of 1 kg ball = m(2v) = 2 mv momentum of 10 kg ball = (10m)v = 10mv

A different scaffold that weighs 400 N supports two painters, one 500 N, and the other 400 N. The tension on the left scale is 800 N. What is the tension in the right-hand scale? A. 1000 N B. 400 N C. 500 N D. 800 N

C. 500 N * The three down (500, 400, 400) equals 1300 N. Subtract 800 from 1300 and you have 500 left over.

With no gravity, the cannonball would follow a straight-line path (green dashed line). But because of gravity, it falls beneath this line the same vertical distance it would fall if it were released from rest. If air resistance isn't a factor and the speed were significantly greater, how much beneath the green dashed line would the cannonball be at 4 seconds? A. 45m B. 60m C. 80m D. None of these

C. 80m * 1/2gt^2 = 1/2 * 10 * 4^2 = 80m

The Equilibrium rule, SigmaF = 0 applies to: A. objects or systems at rest B. objects or systems in uniform motion in a straight line C. Both D. Neither

C. Both *An object that either moves at constant velocity or remain stationary is in equilibrium.

A truck carrying unsecured bales of hay is traveling North on a road. The truck comes to a sharp left curve (west) on the road. As the truck continues traveling along the sharp left curve, the bales of hay start falling off the trunk with A. a westward direction B. an eastward direction C. a northward direction D. a southward direction

C. a northward direction * the truck and bales of hay initially had a northward direction. When the truck started to change direction, the unsecured bales maintained their original motion (north). This is explained by Newton's 1st law of motion.

The concept of inertia is attributed to A. Galileo B. Newton C. Both D. Neither

C. both

Air resistance on a projectile A. lessens its range; B. lessens its height; C. both of the above; D. None of the above.

C. both of the above

Whereas impulse involves force and time, work involves force and A. power B. acceleration C. distance D. time

C. distance * W= F * d

A car is pushed and undergoes a certain acceleration. Consider how the acceleration would compare if it were pushed twice the net force while its mass decreased to half. Then its acceleration would be A. twice B. half C. four times D. none of the above

C. four times * a= F/m 2F/m/2 = 4 F/m = 4a

When a 10-kg falling object encounters 10 N of air resistance, its acceleration is A. g B. more than g C. less than g D. unknown

C. less than g * any object that encounters air resistance accelerates at less than g

If the Sun were twice as massive, its pull-on Earth would be A. four times as much. B. half as much. C. twice as much D. unchanged.

C. twice as much * Based on the equation for gravity, when one mass is doubled, the force doubles

When no air resistance acts on a projectile, its horizontal acceleration is A. g B. less than g C. more than g D. 0.

D. 0 *Horizontally, no force exerts on the object, so it travels with constant velocity along this direction

On rollerblades, you toss a ball horizontally away from you. The mass of the ball is one-tenth your mass. Compared with the speed you give to the ball, your recoil speed will ideally be A. 100 times as much B. 10 times as much C. the same D. 1/10 as much

D. 1/10 as much

For an experiment, you buy a 0.283-kg cube of Silver for $151. The cube's length is 0.0300 meters giving it a volume of 2.70 X 10 - 5 cubic meters. Calculate the cube's Density {kg/m3 } using the following formula: 𝜌= m/v A. 9.54 × 10^−5𝑘g/𝑚3 B. 1.05 × 10^−6kg/𝑚3 C. 9.43 𝑔/𝑚3 D. 10,500 𝒌g/𝒎^3

D. 10,500 kg/m^3 0.283 kg/ 2.70 * 10^-5 m3 = 10500kg/m^3

A 2.27-kg Physics textbook was knocked off a tabletop and fell 0.922 meters to the ground. Just prior to hitting the ground, its speed was 4.25 m/s. Calculate the textbook's kinetic energy just prior to hitting the ground. Kinetic Energy is defined as: KE = 0.5 * mass * (speed)^2 A. 0.961 J B. 41.0 J C. 4.82 J D. 20.5 J

D. 20.5 J * KE= (0.5)(2.27 kg)(4.25 m/s)^2 = 20.5 J

When both the force and time of contact are doubled, the impulse on an object is A. Decreased B. Same C. Doubled D. Quadrupled

D. Quadrupled * 2F * 2t = 4Ft

A projectile follows a curved path: A. when it crosses a gravitational field. B. due to a combination of constant horizontal motion and accelerated downward motion. C. called a parabola. D. All of the above.

D. all of the above

In a circular orbit, the gravitational force on a satellite is A. constant in magnitude; B. at right angles to satellite motion; C. directed toward Earth; D. All of the above.

D. all of the above

The concept of free-falling objects applies to A. falling apples; B. the Moon; C. fired-out cannonball; D. all of the above.

D. all of the above

You are weightless when you are A. in free fall; B. without a support force; C. infinitely away from all mass; D. all of the above.

D. all of the above * An object is weightless because there is no Normal Force supporting it underneath

A model airplane moves 3 times as fast as another identical model airplane. Compared with the kinetic energy of the slower airplane, the kinetic energy of the faster airplane is A. the same for level flight. B. twice as much. C. four times as much. D. more than four times as much.

D. more than four times as much * KE = 1/2 mv^2 *the three times as fast airplane has 9 times as much kinetic energy

The force that directly propels a motor scooter along a highway is that provided by the A. engine B. fuel C. tire D. road.

D. road * the tires push back on the road, and in doing so, the road pushes forward on the tires.

A grasshopper has a head-on collision with a speeding Mack truck. The greatest force acts on the A. truck B. bug C. not enough information D. same amount on each

D. same amount on each * Newton's third law

T or F: A 375-pound concrete cylinder has a base area of 144 square inches. With the cylinder resting on its base, the pressure exerted by the concrete cylinder is greater than Sea Level Pressure (i.e., 14.7 psi). The formula for pressure is P = F/ A

False * 375 / 144 = 2.60 Pa

T or F: Meteorologist use a thermometer to measure atmospheric pressure

False * Barometer

T or F: Two motorcycles, one is 250 pounds the other is 500 pounds, are parked in front of a restaurant. The 500-pound motorcycle has a larger momentum than the 250-pound motorcycle while they are parked at the restaurant.

False. They both have zero momentum because they are at rest Momentum = mass x velocity

T or F: If an object's mass decreases, then its Inertia increases.

False. The less massive an object is, the lower its inertia. Vice versa.

Father of Modern Science

Galileo Galilei

The kind of speed you read on a speedometer is: A. Average speed B. Instantaneous speed C. Changing speed D. constant speed

Instantaneous speed

Traver's home is 6 miles away from his school. If he bikes from home at 15mph, how long does it take him to arrive at school? The answer needs to be in minutes.

v= d/t -> t= d/v -> 6/15 = 2/5= 0.4h 0.4h = 0.4 * 60 mins = 24 mins It takes Traver 24 mins to bike from school to home.