Physics Exam 1

You are on a bus that is moving east at 30 m/s relative to the ground and you are walking toward the back of the bus at of 2 m/s relative to the bus.What is your velocity relative to the ground?

28 m/s east

Light travels in a straight line at a constant speed of 300,000,000 m/s. Therefore acceleration of light is ____ m/s/s. (Hint: Is velocity constant? )

0

You are in your car at the traffic light. What is your instantaneous velocity just before you see green light? (Answer is a number)

0.0

A train starts moving from rest and picks up a speed of 30 m/s in 100 seconds. What is the acceleration of the train (in m/s/s).

0.3

You cycle for 5 km in 30 minutes. Find average speed. Is it possible to find average velocity for this question. (You need to convert time to hours first.)

10 km/h, impossible to find average velocity

Find the distance (in meters) between points A(4m, 9m) and B(4m, -1m) on a coordinate plane(drawing coordinate plane with given points might help).

10.0

A car is going East at 55 mph, a truck is going west at 50 mph. Relative speed of approach is____ mph. If initially the distance between them is 315 miles, they will meet in ____ hours.

105, 3

The width of a square painting on a rocket wall is 90 cm. The rocket is moving at 99% of speed of light flies by the earth. What would be the width and length of the painting according to a stationary observer on the ground?

12.7 cm by 90 cm

How far is our sun from earth if it takes light 8.1 minutes (486 seconds) to reach us? Speed of light is 300,000,000 m/s.

146 million km

The police officer, motionless relative to earth, measures the relative speed between the police car and the other car as 100 km/h. What would the relative speed be if the police officer measured the speed while driving at a constant speed of 50 km/h in the direction opposite to that of the other car?

150 km/h

A boat heads west at a speed of 3.5 m/s (with respect to the river) in a river that is flowing east at a speed of 1.2 m/s (with respect to the ground). Find the velocity of the boat with respect to the stationary observer on the ground.

2.3 m/s, west

Two trains are departing from the same station in the opposite direction. Both of them have constant speed of 70 mph. What would be distance between them in 2 hours?

280 miles

Two cars are driving in the same direction. The one in front at 40 miles per hour and the one behind at 50 miles per hour. In how many hours will the second car catch up if the distance between them is 30 miles?

3

Astronomers have observed a distant galaxy moving away from the Milky Way galaxy at a speed of about 10% of speed of light (30 000 000 m/s). At what speed does the distant light reach the astronomers?

300 000 000 m/s

Someone shines a light while moving toward you at a speed of 1000 m/s. With what speed will the light strike you? (The speed of light is 300 000 000 m/s.)

300 000 000 m/s

An airplane which has a velocity of 400 km/h, east, relative to the ground is flying in a wind with a velocity relative to the ground or 50 km/h, east. What is the velocity of the airplane relative to the wind? (This speed is called the airspeed of the airplane)

350 km/h, east

A marathon runner runs at a speed of 12 miles per hour. What distance will she cover (in miles) in three hours?

36

Elliot is traveling by a building at 150 000 000 m/s, moving along the width of the building. A person standing at rest next to the building measures the building to be 50 m wide and 100 m tall. What is the height and width of the building as measured by Elliot? (We did not have time during the lecture to go through the detailed solution to this question, so I have just uploaded solution on the next slide)

43 m wide and 100 m tall

An observer sitting on a spaceship that is moving at 85% of speed of light times an event to last 30 seconds, what is the corresponding time elapsed according to a second (stationary) observer's clock on earth?

57s

You wish to travel from St. Louis to Chicago (about 462 km away). If you average 77 km/h, how many hours will the trip take?

6.0

You take your pulse while on a fast moving train and you measure 60 beats per second. All else being equal, what would you measure if you measured your pulse while standing on the ground instead?

60 beats per second

If you walk at 1 km/ h down the aisle toward the front of a train that moves at 60 km/h, your speed relative to the ground is ____ km/h.

61

A bug starts motion on a straight rope at x = 2 m. It climbs 4 m right, 1 m left and 2 m right. The bug's final position is x = ___ meters (to the right) from the origin, it's displacement is meters _____ right, and the distance traveled by the bug is _____ meters.

7, 5, 7

A red car moves north at 40 m/s and a green car moves at 30 m/s, south. If they start from the same location, what is their relative speed of recession? Does this relative speed of recession depend on whether the observation is made from the ground, from the red car or from the green car?

70 m/s. No, it is not dependent on the choice of reference frame.

A car is going west at a constant speed of 60 m/s. How many kilometers will it cover in 20 minutes? Hint: final answer should be in KILOMETERS. Also be careful with units, speed is in meters per SECOND and time is given in MINUTES.

72.0

A race car completes a 4 mile circular track in 90 seconds. Find its average speed. Find its average velocity. Did the car accelerate during the 90 seconds? (Hint: before you use the formula convert time to hours, because answers are given in "mph")

Average speed is 160 mph. Average velocity is 0 mph. It is accelerating.

You decide to run around a circular path of 3 km (3000 meters). You take 10 minutes (600 seconds) to complete each revolution. You run once along this path, what is the average speed and average velocity for this trip?

Average speed is 5 m/s and average velocity 0 m/s

A tortoise is slowly moving right at a constant velocity. Which inertial reference frame is more valid? Reference frame attached attached to tortoise or A reference frame attached to ground

Both

One airplane travels north at 200 km/h while another travels south at 200 km/h.Pick the correct statements from below:

Both airplanes have the same speeds and different velocities.

You take your pulse while sitting in your room and you measure 60 beats per second. All else being equal, what would your pulse measure if you took it while on a fast moving train?

It would measure the same

Where is Mrs Nino's office located?

Cardwell 20, ground floor

What two possibilities for change in an object's motion results in its acceleration?

Change in the speed and change in its direction of motion.

Which of the following represents a vector quantity: time, length, height, mass, displacement, distance, and area.

Displacement

You walk to your mailbox 15 meters directly across your door you take the letters and go back to the door. What is your distance and displacement?

Distance 30 m, displacement 0 m

Which of the following represents a Scalar quantity: time, length, height, mass, displacement, distance, and area.

Distance and Mass

Is a fine for speeding based on one's average speed or instantaneous speed?

Instantaneous speed

As you drive at 60 mph, north, you see a car driving 60 mph, east. Does the other car have the same speed as you? Does it have the same velocity as you?

It has the same speed but different velocity

As speed increases for an objects in free fall, does acceleration also increase?

No

Can an object be moving with 600 000 000 m/s. (speed of light c = 300 000 000 m/s)

No

A bowling ball and a basketball are released from the same height in a vacuum chamber. Which object will hit the ground first

Same time

If the cup below was inside a spaceship that is moving right at high speed, with respect to earth, what would observer on earth see.

The cup would seem narrower

If a cargo falls out of the plane which is moving right,(with constant velocity), where will it land?

To the right from the location of the plane at the moment of release.

In which of the following scenarios is the instantaneous velocity at any moment in time more likely to be different from average velocity? Traveling within a city with lots of busy traffic and lots of traffic lights or Traveling between two cities by car, on an almost empty highway

Traveling within a city with lots busy traffic and lots of traffic lights.

Maria is jogging at a velocity of 4 m/s, east. David is 12 m behind her, running at a velocity of 3 m/s, east. Both velocities are relative to the earth. What is David's velocity relative to Maria? In how many seconds will the distance between them be 18 m?

V relative = 1 m/s, west. In 6 seconds

If object is moving with a constant velocity, is its instantaneous velocity equal to its average velocity?

Yes

Does length contraction occur with speeds that are much slower than speed of light?

Yes but we will not be able to measure the effect, since its so small.

Due to length contraction, you notice that train passing by appears to be shorter than when it is stationary. What do people on the train observe about you?

Your width is less

Which of the following objects are in uniform (constant velocity) motion and which are in accelerated motion? a) A boat heading west at at 25 mph. b) A bus going around a curve at 30 mph. c) A notebook resting on a table. d) Earth revolving around sun.

a, c - uniform; b, d - accelerated motion

I was jogging, north at 3 m/s and gradually slowed down to 2 m/s, north, during the period of 4 seconds, what was my acceleration? Treat north as positive direction.

negative 0.25 m/s/s, ( or 0.25 m/s/s, south)