Physics Midterm

Refer to study guide #62

-14.0kg*m/s 5x8=40 4x15=60 2x3=6 40-60=-20 -20+6=-14

Refer to number 67 on study guide.

-30J

What is 0.674 / 0.74 to the proper number of significant figures?

0.91

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

28km Square root 20^2+20^2= 28

You throw a rock horizontally off a cliff with a speed of 20m/s and no signifigant air resistance, what is the speed of the ball when it returns to the same horizontal level?

28m/s

Refer to study guide #40

2m X intercept of T

The length and width of of a rectangle are 1.125 m and 0.606 m, respectively. You calculate the rectangles perimeter by adding these numbers and multiplying by two. Your calculators display reads 3.462. To the correct number of signifigant figures, the perimeter should be written as...

3.462

Add 1299 g and 45.1 kg and express your answer in milligrams (mg) to the correct number of significant figures.

4.64 x 10^7

A crane lifts a 425 kg steel beam vertically upward a distance of 95m. How much work does th crane do on the beam if th beam accelerates upward at 1.8m/s^2? Neglect frictional forces.

4.7x10^5J

In a shuffleboard game, the puck slides a total of 12m on a horizontal surface before coming to rest. If the coefficient of kinetic friction between the puck and board is .1, what is the initial speed of the puck?

4.8m/s -.1(9.81)=-.98m/s^2 0=vi^2 +2(-.98x12) V=4.8

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?

4.8m/s 7^2=a^2+5.1^2 A^2= 4.8

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

5 m/s 2pi49=307.9 2x96=192+307.9=499.9 499.9/100= 5

A football field is 120 yd long and 50 yd wide. What is the area of the football field, in square meters? (1.0yd= 91.44cm)

5.0 x 10^3 120 x 91.44 = 10972.8 50 x 91.44 = 4572 10972.8 x 4572 = 5.0 x 10^3

Calculate the average Force a bumper would have to exert to bring a 1200kg car to rest in 15cm when the car had an initial speed of 2 m/s.

6.5x10^5 1/2(1200)x(0^2-2^2)=F(15)

A block of mass m = 3.6 kg, moving on a frictionless surface with a speed makes a sudden perfectly elastic collision with a stationary block of mass M, as shown in the figure. Just after the collision, the 3.6-kg block recoils with a speed of What is the speed V of the other block?

6.6m/s

What is the sum of 1.53 + 2.786 + 3.3?

7.6

Refer to chart for #33

Choice 4

Refer to study guide for number 30

Choice c

In a collision between a huge SUV and a small hybrid car, the SUV exerts a larger force on the hybrid car than th hybrid exerts on the SUV (t/f)

False

Two displacement vectors have magnitudes of 5.0 m and 7.0 m, respectively. When these two vectors are added, the magnitude of the sum

Is could be 2m or 12m

Suppose that a car traveling to the west begins to slow down as it approaches a traffic light. Which of the following statements about its acceleration is correct?

The acceleration is towards the east.

A 50g ball moving at 10m/s in the +x direction suddenly collided head on with a stationary ball of mass 100g. If the collision is perfectly elastic, what is the velocity of each ball immediately after the collision?

-3.3m/s, +6.7m/s

Refer to question 72 on study guide.

-75kg*m/s

An ornament of mass 40.0 g is attached to a vertical ideal spring with a force constant (spring constant) of 20.0 N/m. The ornament is then lowered very slowly until the spring stops stretching. How much does the spring stretch?

.0196

During a hockey game, a puck is given an initial speed of 10 m/s. It slides 50 m on the ice before it stops. What is the coefficient of kinetic friction between the puck and the ice?

.10 0=10^2+2xax50 0=100+100a a=-1 -1/9.81= .102

A 0.330kg volleyball is thrown vertically downward with a speed of .150m/s in a place where g=9.81m/s^2. It takes 0.0655s to reach the ground. What is the magnitude of its momentum just before it hits the ground?

.262 kg*m/s

A car traveling north at 17.7 m/s. After 12s its velocity is 14.1 m/s in the same direction. Find the magnitude and direction of the cars average acceleration.

.30 m/s^2, south 17.7-14.1=3.6 3.6/12=.3

Refer to study guide for #16

.67 m/s

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 velocity?

0 m/s

Two ice skaters suddenly push off against one another starting from a stationary position. The 45-kg skater acquires a speed of 0.375 m/s relative to the ice. What speed does the 60-kg skater acquire relative to the ice?

0.28m/s (45x0.375)/60= .28

A 0.14-kg baseball is dropped from r st from a height of 2.0 m above the ground. What is the magnitude of its momentum just before it hits the ground if we neglect air resistance.

0.88kg*m/s

Refer to #66 on study guide

0J

Refer to study guide #39

0N

A 340-g air track cart traveling at 1.25m/s suddenly collides elastically with a stationary 300-g cart. What is the speed of the 300-g cart just after collision?

1.33m/s ((2x340)/340+300))1.25 =1.33

A 320-g air track cart traveling at 1.25m/s suddenly collides elastically with a stationary 270-g cart. What is the speed of the 270-g cart just after collision?

1.36m/s ((2x320)/320+270))1.25 =1.36

Refer to study guide#28

1.7m/s^2

A train travels at a constant speed of 60.4 mi/h for 101.5 min. What distance does the train cover in the correct number of signifigant figures?

102 mi. 60.4/60=1.00667x101.5

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

10m/s 1/2 (20)

If a net force accelerates a 4.5kg tool at 40m/s^2, what acceleration would that same net force give to an 18kg tool?

10m/s 4.5x40=180 180/18=10

The x component of vector A is 8.7 units, and its y component is -6.5units. The magnitude of A is closest to

11 units

Refer to question 53 on study guide

12 and 90 kg

A policeman investigating an accident measures the skid marks left by a car. He determines that the distance between the point that the driver slammed on the brakes and the point where the car came to a stop was 28.0 m. From a reference manual he determines that the coefficient of kinetic friction between the tires and the road under the prevailing conditions was 0.300. How fast was the car going when the driver applied the brakes? (This car was not equipped with anti-lock brakes.)

12.8m/s Friciton force = Ff = uFn = 0.3*m*9.81 since F = ma .3*9.81*m = ma mass cancels out a = 2.93 m/s^2 velocity of the vehicle: v^2 = 2*a*d = 2*2.94*28 = 165 m/s v = 12.8 m/s

An instrument is thrown upward with a speed of 15m/s on the surface of Planet X where the acceleration due to gravity is 1.5m/s^2 and there is no atmosphere. How long does it take for the instrument to return to where it was thrown?

12s -(2*15)/-2.5=12s

Refer to question 37

13

A car is moving with a speed of 32m/s. The driver sees an accident ahead and slams on the brakes, causing the car to slow down with a uniform acceleration of magnitude 3.5m/s^2. How far does does the car travel after ther driver put on the breaks until it comes to a stop?

146m 0=32+-3.5t T=9.143s Xf=0+32(9.148)+1/2(-3.5)(9.143)^2 Xf=146

A 328kg car moving at 19.1 m/s in the +x direction hits from behind a second car moving at 13m/s in the same direction. If the second car has a mass of 790kg and a speed of 15.1m/s right after the collision, what is the velocity of th first car after this sudden collision?

14m/s (328x19.1+790x13-790x15.1)/328

A car heading north suddenly collides at an intersection with a truck of the same mass heading east. If they lock together and travel at 28m/s at 15degrees north of east just after the collision, how fast was the car initially traveling?

14m/s 2(28sin15)=14 **make sure you're in degree mode**

A 600-kg car makes a 90degree turn. It's speed before the turn is 21m/s and after the turn is 24m/s. What is the magnitude of change in the cars momentum during th turn?

19.1x10^3

On its own, a tow truck has a maximum acceleration of 3.0 m/s^2. What will be its maximum acceleration when the truck is using a light horizontal chain to tow a bus of twice its own mass?

1m/s 3/3=1

In the product A*B*C, A has 5 significant figures, B has 2 significant figures, and C has 3 significant figures. How many significant figures does the product have?

2

In the sum, A+B+C, A is accurate to 5 decimal places, B is acurate to 2 decimal places, and C is acurate to 3 decimal places. What is the correct number of decimal places in the sum?

2

Refer to #52 on study guide

2.5g .5/200=.0025 2.5

An object that weighs 75N is pulled on a horizontal surface by a horizontal pull of 50N to the right. The friction force on this object is 30N to the left. What is the acceleration of this object?

2.6m/s^2 75/9.8=7.65 50-30=20 20/7.65=2.6

A baseball player is running to second base at 5.03m/s. When he is 4.8m from the plate, he goes into a slide. The coefficient of kinetic friction between the player and the ground is .180. The coefficient of static friction is 3.14. What is his speed when he reaches the plate?

2.89

What is the product of 12.56 and 2.12 expressed to the correct number of significant figures?

26.6

To determine the height of a bridge above the water, a person drops a stone and measures the time it takes for it to hit the water. If the time is 2.3s, what is the height of the bridge? Neglect air resistance.

26m 2.3^2=5.29 1/2*9.8*5.29=26

A car starts from rest and accelerates at a steady 6.00m/s^2. How far does it travel in the first 3.00s?

27m Xi = 0+1/2(6)(3)^2= 27

An astronaut stands by the rim of a crater on the Moon, where the acceleration of gravity is 1.62 m/s2 and there is no air. To determine the depth of the crater, she drops a rock and measures the time it takes for it to hit the bottom. If the time is 6.3s, what is the depth of the crater?

32m 1/2*1.62*6.3^2=32

A proton of mass m is at rest when it is suddenly struck head on by an alpha particle (which consists of 2 protons and 2 neutrons) moving at speed v. If the collision is perfectly elastic, what speed will the alpha particle have after the collision? (Assume the neutrons mass is equal to the protons mass).

3v/5

A car initially traveling at 60km/h accelerates at a constant rate of 2.0 m/s^2. How much time is required for ther car to reach the speed of 90km/h?

4.2s 2x60x60=7200/1000=7.2 30/7.2=4.2

Leonardo da Vinci's Mona Lisa is 21 in wide, and 30.25 in. Tall. What is the area of the painting in square centimeters? (1.00m = 39.37 in.)

4100 cm^2 21/39.37= .533 30.25/39.37= .768 53.3 x 76.8 = 4093

A 900-kg car traveling east at 15.0 m/s suddenly collides with a 750kg car traveling north at 20.0m/s. The cars stick together after the collision. In what direction does the wreckage move just after the collision?

48degrees N of E

A light-year is the distance that light travels in one year. The speed of light is 3.00 x 10^8 m/s. How many miles are there in one light year? (1mi = 1609m, 1y=365d)

5.88x10^12mi 60 seconds/minute x 60 minutes/hour x 24 hours/day x 365.26 days/year = 3.16 x 10^7 seconds/year (3.00x10^8)/1609 = 1.86x10^5 (1.86x10^5)x(3.16x10^7)= 5.88x10^12

Astronaut Jennifer's lifeline to her spaceship come loose and she finds herself stranded, "floating" 100m from the mothership. She suddenly throws her 2.00kg wrench at 20m/s in a direction away from the ship. If she and her spacesuit have a combined mass of 200kg, how long does it take her to coast back to her spaceship?

500s 100/.2= 500

An astronaut weighs 99.0 N on the Moon, where the acceleration of gravity is 1.62 m/s2. How much does she weigh on Earth?

600N 99/1.62 = x/9.81 X=600

You walk 53m to the north, then you turn 60degrees to your right and walk another 45m. Determine the direction of your displacement vector. Express your answer as an angle relative to east.

63 NofE Bx= 45cos30=39 By= 45sin30=22.5 39+22.5= 63

Refer to study guide #41

66degrees below the x axis

A cart with an initial velocity of 5.0m/s to the right experiences a constant acceleration of 2.0m/s^2 to the right. What is the carts displacement during the first 6s of this motion?

66m 0+5(6)+1/2(2)(6)^2=66

What must be your average speed in order to travel 350 km in 5.15 h?

68.0 km/h 350/5.15 = 68

What is the mass of an object that experiences a gravitational force of 685N near earths surface where g=9.8m/s^2

69.9kg 685/9.8=69.9

A 900-kg car traveling 30degrees south of east at 12m/s suddenly collides with a 750 kg car traveling north at 17m/s. The cars stick together after the colliding. What is the speed of the wreckage just after the collision?

7.21m/s the north direction the total initial momentum = 750*17 - 900*12 sin 30 = 7350 kgm/s In the east direction the total initial momentum = 900*12cos 30= 9353.07 If V is the velocity of both together, then its component in the east direction V cos θ = 9353.07/ (900+750) = 5.7 m/s Square root of 5.7^2+4.45^2

A ball is thrown downward from the top of a building with an initial speed of 25m/s. It strikes the ground after 2s. How high is the building, assuming air resistance is negligible.

70m 0=xi-25*2+1/2(-9.81)(2)^2 Xi=67.72

An airplane undergoes the following displacements, all at the same altitude: First, it flies 59km in a direction 30degrees east of north. Next, it flies 58km due south. Finally it flies 100km 30degrees north of west. Use components to determine how far the airplane ends up from its starting point.

71.5km

Refer to study guide for 34

77 degrees Tan^-1(6.1/9.2)=33.5 Tan^-1(4.3/4.5)=43.6 33.5+43.6=77

Th coefficients of static and kinetic friction between a 3.0kg box and a horizontal desktop are .4 and .3, respectively. what is th force of friction on the box when a 15N horizontal push is applied to the box?

8.8N .3x3x9.8=8.8

A child does 350J of work while pulling a box from the ground up to his tree house at a steady speed with a light rope. The tree house is 4.0m above the ground. What is the mass of the box?

8.9kg 350=9.81m(4) m=8.9

A ball is thrown at an original speed of 8m/s at an angle 35degrees above the horizontal. If we can neglect air resistance, what is the speed of the ball when it returns to the same horizontal level?

8m/s

A laser is thrown upward with a speed of 12m/s on the surface of Planet X where the acceleration due to gravity is 1.5m/s^2 and there is no atmosphere. How long does it take for the laser to reach maximum height.

8s 12=0+1.5t T=8

A rubber ball and a lump of clay have equal mass. They are thrown with equal speed against a wall the ball bounces back with nearly the same speed with which it hit. The clay sticks to the wall. Which of these objects experiences the greater momentum change?

The ball

Suppose that an object travels from one point in space to another. Make a comparison between the displacement and the distance traveled.

The displacement is either less than or equal to the distance traveled.