### PHYSICS MIDTERM

68.0 km/h

what must your average speed be in order to travel 350 km in 5.15 hr?

4.44 h

A car travels 90km/h. How long does it take for it to travel 400km?

infinite speed

If the position versus time graph of an object is a vertical line, the object is?

moving at a constant, non-zero speed

if the velocity versus time graph of an object is an horizontal line, the object is?

180 degrees (opposite direction)

the resultant of two vectors is the smallest when the angle between them is how many degrees?

20 m/s

If a ball is thrown with a velocity of 25m/s at an angle of 37 degrees above the horizontal, what is the horizontal component of the velocity?

71.56 degrees

If you walk 6.0 km in a straight line in a direction north of east and you end up 2.0km east and several kilometers north. How many degrees north have you walked?

17^1/2 (square root of 17)

Two vectors A and B have components (0,1) and (-1,3), respectively. What is the magnitude of the sum of the two vectors?

28.28 km

A car travels 20km west, then 20km south. What is the magnitude of its displacement?

20 m

A runner runs halfway around a circular path of radius 10m. What is the displacement of the jogger?

vector- magnitude and direction

scalar- only magnitude

scalar- only magnitude

What is the difference between vector and scalar quantities?

20.2 m

A girl throws a rock horizontally, with a velocity of 10m/s from a bridge. It falls 20m to the water below. How far does the rock travel horizontally before striking the water?

318 m

A projectile is launched with an initial velocity of 60.0m/s at an angle 30 degrees above the horizontal. How far does it travel?

increase

A package of supplies is dropped from a plane and one second later a second package is dropped. Neglecting air resistance, the distance between the falling packages will?

be above the bomb

A pilot drops a bomb from a plane flying horizontally. When the bomb hits the ground, the horizontal location of the plane will?

9.8m/s^2 downward

A soccer ball is kicked with a velocity of 25m/s at a 45 degree angle above the horizontal. What is the vertical component of its acceleration as it travels along its trajectory?

the stone

A stone is thrown horizontally from the top of a tower at the same instant a ball is dropped vertically. Which object is traveling faster when it hits the level group below?

30 and 60 degrees

An Olympic athlete throws a javelin at four different angles above the horizontal, each with the same speed: 30 degrees, 40 degrees, 60 degrees and 80 degrees. Which two throws cause the javelin to land the same distance away?

remains constant

Ignoring air resistance, what is the horizontal component of a projectile’s velocity?

8.3333 or 8.22m/s

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

750s

On a calm day(no wind), you can run a 1500-m race at a velocity of 4.0m/s. If you ran the same race on a day when you had a constant headwind which slows your speed by 2.0m/s the time it would take you to finish would be?

123.693km/h

An airplane with a speed of 120km/h is headed 30 degrees east of north in a wind blowing due east at 30km/h. What is the speed of the plane relative to the ground?

1st law – object in motion with stay in motion

Which of newtons laws best explains why motorists should buckle-up?

50kg

What is the mass of a person who weighs 110lbs?

A/2

A net force “F” accelerates a mass “M” with acceleration “A”. If the same net force is applied to mass “2M”, then the acceleration would be?

the velocity decreases

You are standing in a moving bus, facing forward, and you suddenly fall forward. You can imply from this that the bus’s_______?

neither the ratios are the same

Who has a greater weight to mass ration, a person weighing 400N or a person weighing 600N?

3 forces

What is the total number of forces acting on a car parked on a hill (with parking brakes on) is?

2 forces

The number or forces acting on a car parked on a hill (with parking brakes released) is?

zero

When you sit on a chair the resultant force on you is?

Newton’s 3rd law – for every action there is an opposite and equal reaction

If you blow up a balloon and then release it, the balloon will fly away. This is an example of which of Newton’s Laws?

the object pulling upward on the Earth with force is mg

an object of mass “m” sits on a flat table. The Earth pulls on this object with a force of “mg” which we will call the action force. What is the reaction force?

states in which opposing forces or influences are balanced

How would describe an object in equilibrium?

the feather

A brick and a feather fall to the Earth at their respective terminal velocities. Which object experiences the greater force of air resistance?

the toy pulling upward on the earth with an 8N force

A child’s toy is suspended front he ceiling by means of a string. The earth pulls downward on the toy with its weight force of 8.0N. IF this is the “action force” what is the reaction force?

the net force is = to mg

A stone is thrown straight up. At the TOP of its path, the NET FORCE acting on it is?

both cars accelerate at the same rate (0.5)

Two toy cars (16kg and 2.0kg) are released simultaneously on an inclined plane that makes an angle of 30 degrees with the horizontal. What happens to their acceleration after being released?

8kg

An object sits on a frictionless surface. A 16N force is applied to the object and it accelerates at 2.0m/s. What is the mass of the object?

2A

A net force “f” acts on a mass “m” and produces acceleration “a”. What acceleration results if a net force “f/2” acts on mass “4m”?

-3.0 N

A horizontal force of 5.0N accelerates a 4.0kg mass, from rest at a rate of 0.50m/s2 in the positive direction. What friction force acts on the mass?

294

A person on a scale rides in an elevator. IF the mass of the person is 60.0kg and the elevator accelerated upward with an acceleration of 4.90, what is the reading on the scale?

3.9 x 10^3N

A sports car of mass 1000kg can accelerate from rest to 27m/s in 7.0s. What is the average forward force on the car?

17N

A 10kg mass slides down a flat hill that mass an angle of 10 degrees with the horizontal. if friction is negligible what is the resultant force on the sled?

exactly mg

An object of mass “m” is hanging by a string from the roof of an elevator. The elevator is moving up at a constant speed. What is the tension in the string?

332 N

A student pulls a box of books on a smooth horizontal floor with a force of 100N in a direction of 37 degrees above the horizontal. IF the mass of the box and the books is 40.0kg, what is the normal force on the box?

coefficient = 0.25

an object slides on a level surface in the x direction it slows and comes to a stop with a constant acceleration of -2.45m/s2. What is the coefficient of kinetic friction between the object and the floor?

1/5 m/s2

A 10kg box is sitting on a horizontal surface is pulled by a 5.0N force. A 3.0N friction force retards the motion. What is the acceleration of the object?

4m/s2

An object moves with a constant speed of 20m/s on a circular track of radius 100m. What is the acceleration of the object?

42.43 km/h

The maximum speed around a level curve is 30.0km/h. What is the maximum speed around a curve with twice the radius?

6m/s2

A car goes around 150m radius curve with a constant speed of 30m/s. What is its acceleration?

0.95

How many revolutions per minute must a circular, rotating space station of radius 1000m rotate to produce an artificial gravity of 9.80m/s2?

centripetal force

What type of force is needed to make and object move in a circle?

towards the center of the curb

A car goes around a curve of radius r at a constant speed v. What is the direction of the newt force on the car?

force is 1/4 as big

If a car goes around a curve at half the speed, what happens to the centripetal force on the car?

moving in a circle

Describe the motion of a particle moving with constant speed such that its acceleration of constant magnitude is always perpendicular to it velocity.

31.321m/s

A frictionless curve of radius 100m, banked at an angle of 45 degrees, may be safely negotiated at what speed?

work in unit is joules

what is the correct unit of work?

10 J

You lift a 10N physics book up in the air a distance of 1.0m at a constant velocity of 0.50 m/s what is the work done by the weight of the book?

29,750 J

A 500kg elevator is pulled upward with a constant force of 5500N for a distance of 50.0m. What is the work done by the 5500N force?

no work cannot be done

Can work be done on a system if there is no motion?

none-no motion

A 50 N object was lifted 2.0m vertically and is being held there. How much work is being done in holding the box in this position?

it would skid 4 times farther

You slam on the brakes of your car in a panic, and skid a certain distance on a straight, level road. If you had been traveling twice as fast, what distance would the car skidded, under the same conditions?

735W

At what rate is a 60.0kg boy using energy when he runs up a flight of stairs 10.0m high, in 8.00s?

90 horsepower

A 1500kg car accelerates from 0 to 25m/s in 7.0s. What is the average power delivered by the engine? (1hp = 746 W)

the unit of power is watts

what is the unit of power?

no, the force and displacement of the object are perpendicular

Does the centripetal force acting on an object do work on the object?