Physics Exam 1

A 3.0-kg cat runs to the left at 10 m/s and a 10-kg dog runs to the right at 4.0 m/s. The total kinetic energy is

230 Joule

If you were standing on a cart that was at rest and free to roll (ignore friction) and someone threw a 10 kg ball at you, you would

roll backward faster if the ball bounced off you elastically

A quantity that is measured of how the distance traveled changes with time is

speed

The mass of an apple on the Earth is 0.2 kg. On the Moon, the mass of the same apple would be

0.2 kg

A student releases a ball from rest on an inclined plane and measures that it travels a distante of 0.8 m in a time of 3.2 s. The average speed of the ball is

0.25 m/s^2

Suppose you climb the stairs of a ten-story building, about 30 m high, and your mass is 60 kg. The potential energy you gain is about

18000 Joule

In a laboratory on Earth, all the air is pumped from a large tube. A feather and a steel ball are simultaneously released from rest inside the tube. What happens next?

Both objects fall and hit the bottom at the same time

As a car drives with its tires rolling freely without any slippage, the type of friction acting between the tires and the road is

static friction

You stand on a scale to measure your weight. The reaction to the force the Earth exerts on you is

the force you exert on the Earth

If you are launching a matchstick rocket, the action force is the rocket pushing the gases down. What is the reaction force?

the gases pushing the rocket up

A gun is made of a super-low weight but strong material. The bullet for the gun is more massive than the gun itself. For such a gun

the gun, if unsupported, would have a recoil velocity higher than the bullet velocity

A ball at the end of a string is swinging as a simple pendulum. Assuming no loss in energy due to friction, we can say for the ball that

the potential energy is maximum where the kinetic energy is a minimum

A ball thrown upward reaches its maximum height and then falls back. If air resistance is negligible, its acceleration is

the same at all points in the motion

A car is traveling at the velocity of 20 m/s on a flat road when it reaches the bottom of a hill. It coasts up the hill, coming to rest in 8 seconds. The average acceleration of the car while on the hill is

-2.5 m/s^2

Two students have a "tug-of-war" on a smooth gym floor. One student has a mass of 70 kg and is wearing socks but no athletic shoes. The other student has a mass of 60 kg and is wearing athletic shoes. The student most likely to win will be:

the 60 kg student because he has greater frictional force

Two cars are moving around a circular track at the same constant speed. If car 1 is at the inner edge of the track and car 2 is at the outer edge, then

the acceleration of car 1 is greater than the acceleration of car 2

A car travels around a curve with constant speed. The correct statement from the following is

the car has an acceleration directed inward toward the center of the curve

When a net horizontal force of 250 N acts on a 50-kg cart that is free to roll on a level surface

the cart accelerates at 5 m/s^2

For a 0.1 kg frog to jump to a height of 1.0 meter requires an energy of about

1.0 Joule

A defensive lineman picks up a fumbled football and begins rumbling toward the end zone. His mass is 150 kg and his velocity is 6.0 m/s west. A wide receiver whose mass is 90 kg must stop the lineman. How fast must the wide receiver be running if he wants to drop the lineman in his tracks

10 m/s

A cyclist races around a circular track at the constant speed of 20 m/s. The radius of the track is 40 m. The centripetal acceleration of the cyclist is

10 m/s^2, toward the center of the track

An 80-kg football player travels to the right at 8 m/s and a 120-kg player on the opposite team travels to the left at 4.0 m/s. The total momentum is

160 kg m/s to the right

A bullet of mass 0.01 kg and speed of 200 m/s is brought to rest in a wooden block after penetrating a distance of 0.10 m. This process takes 0.02 second. The magnitude of the impulse delivered to the bullet by the block during this time is

2.0 Ns

A 30-kg child runs at 3.0 m/s and jumps onto a shopping cart and holds on for dear life. The cart has a mass of 20 kg. Assuming the child rides on the cart after the collision, the speed of the child and shopping cart just after the child jumps on is

2.0 m/s

A calculus book weighing 20 N rests on the floor of a classroom. The reaction to the force of the floor on the book is a force of

20 N exerted by the book on the Earth

In a head-on automobile collision, a person's momentum could be reduced from 2000 kg m/s to zero in just 0.1 s. If this occurs, the average force exerted to stop the person is

20,000 N

A crate is acted upon by a net force of 100 N. An acceleration of 4.0 m/s^2 results. The weight of the crate is

245 N

A box is moved 10 m across by a floor a force of 25 N acting along the direction of motion. The work done by the force is

250 J

A man weighs 650 N while on the surface of Earth. If he is transported to the planet Mythos, which has the same mass as Earth but a radius that is five times larger than Earth's, his weight would be

26 N

If the speed of a car is tripled, the impulse required to stop the car changes by a factor of

3

The average force required to accelerate a 0.20- kg ball from rest to 30 m/s in 0.002 s is

3,000 N

Your car can accelerate at 8.0 m/s^2, and there are 1609 m in one mile. So you can go from zero to 60 mi/hr in about

3.35s

An iron robot falls from rest at a great height. Neglecting air resistance, what is its speed after it has fallen for 3.5 seconds?

34.3 m/s

If your average speed for a 6 hr trip is 60 mi/hr, the distance traveled is

360 mi

If the speed of a car is doubled but the brakes apply the same force, the distance required to stop the car changes by a factor of

4

A 3 kg block initially moving due east at 6 m/s is acted upon by an impulse having magnitude 6 Ns and direction due west. The final velocity of the block is

4 m/s east

A 10.0 kg block on a smooth horizontal surface is acted upon by two forces; a horizontal force of 70 N acting to the left and a hormonal force of 30 N to the right. The acceleration of the block will be

4.0 m/s^2 to the left

A sprinter moving at 10 m/s slows down at a rate of 1.4 m/s^2. How fast is the runner moving after 4 seconds?

4.4 m/s

For identical cannons and identical projectiles and identical initial speeds, but different pointing angles the maximum distance for its projectile is attained for the cannon which launches at

45 degrees above horizontal

A dog weighs 200 N. What is his approximate weight in pounds? (1 lb = 4.45 N)

45 lbs

An object with a kinetic energy of 50 J is stopped in a distance of 0.01 m. The average force that stops the object is

5,000 N

For the first hour a car is driven at a constant speed of 90 km/hr. The motor begins to vibrate and the driver reduces the speed from 45 km/hr for another 2 hours. The average speed for the entire trip is

60.0 km/hr

A body travels at an initial speed of 2.5 m/s. Given a constant acceleration of 0.2 m/s^2, what is the speed of the body at time 25 seconds later?

7.5 m/s

A ball is thrown straight up. It reaches its highest point and then falls back. Which of the following is the correct statement?

At the highest point in its motion, the ball's velocity is zero

Which of the following is not an appropriate unit for measuring acceleration A. miles/hr/s B. ft/s^2 C. m/s D. km/min/s E. m/min^2

C. m/s

Identify the force of friction involved in the two scenarios: Case 1: A force is applied on a book at rest on a table to slide it across Case 2: A shopping cart is pushed to keep moving it around at a constant velocity

Case 1 involved static friction, Case 2 involves kinetic friction

In attempting to pull a 1500 kg car out of a ditch, Al exerts a force of 200 N for 5 s, Bill exerts a force of 500 N for two s, and Clyde exerts a force of 300 N for four seconds. The car does not move at all. Who provided the greatest impulse?

Clyde

A brick slides down a smooth frictionless incline. What happened to the potential energy of the brick?

It was converted to kinetic energy

An acorn falls from a tree. Compare its kinetic energy, K, to its potential energy U.

K increases and U decreases

One form of the proper metric unit for momentum is

N/ sec

A wooden block slides down a rough incline. which of the following statements is true?

The total energy of the block is decreasing

The coefficient of static friction for ice on ice is 0.1, while the coefficient of kinetic friction for ice on ice is 0.03. Based on this information which of these statements is correct?

The force required to overcome kinetic friction is less than the force required to overcome static friction

A quarterback of mass 85 kg is running at 10 m/s. Also, a tackle of mass 100 kg is running at 9 m/s.

The quarterback has the greater kinetic energy

Jim exerts a force of 500 N against a 100 kg desk that does not move. Virgil exerts a force of 400 N against a 60 kg desk that moves 2 m in the direction of the push. Mike exerts a force of 200 N against a 50 kg desk that moves 4 m in the direction of the push. The most work is done by

Virgil and Mik who do equal amounts of work

A body sliding on a table is observed to gradually slow down. The correct statement is that the body slows down because

a net force acts on the body

A quality that is measure of how the velocity of a body changes with time is

acceleration

If you push twice as hard against a stationary brick wall, the amount of work you do

remains constant at zero

Which has the greater kinetic energy? a. a 1 ton car moving at 30 m/s b. a half-ton car moving at 60 m/s c. a 1 ton car d. both have same kinetic energy e. a half-ton car

b. a half-ton car moving at 60 m/s

Describe the energy of a car driving up a hill

both kinetic and potential

The purpose of an air bag in an auto is to

decrease the force applied to you during a collision

Force F, acting for time T and over a distance D, gives impulse I. To get the same impulse using half the force, it would be necessary for the force to act

for a time 2T

A child riding on a swing rises to a height 1.0 m above the lowest point. Another child of equal mass whose speed at the lowest point is twice as great will rise

four times as high

A box is pushed across a rough horizontal floor by a force acting parallel to the floor in the direction of motion. A force doing negative work on the body is

friction

A box is pushed across a rough horizontal floor by a force acting parallel to the floor in the direction of motion. A force doing no work during the motion is

gravity

Car A travels with speed v around curve number one, which has a radius r. Car B travels with speed 2v around curve number two, which has a radius 2r. The acceleration will be

greater for car B

A ball is whirled on the end of a string in a horizontal circle at constant speed. Suddenly, the string breaks. Immediately after the string breaks, the ball will

have a horizontal velocity that is tangential to the circle

A policeman walks on his beat back and forth. His average speed is determined from

his total distance covered divided by the time

The momentum of a truck is increased by a factor of 2; its weight does not change. Thus,

its speed doubled

You travel 2640 feet in 30 seconds while in a 65 mi/hr zone. (There are 5280 ft in one mi.) Your average speed is

less than the speed limit

Two people sit face to face on nice skateboards that are free to roll without friction. They push each other with a force of 40 N and move apart. Person X whose mass (including the skateboard) is 50 kg, moves to the left at 3 m/s. Person Z, whose mass (including the skateboard) is 60 kg

moves to the right at 2.5 m/s

A bullet is fired into a wall and comes to rest. Considering only the bullet as the system we can say that

neither total kinetic energy nor momentum is conserved

Work is not being done on an object unless the

object is moving

Two piece of kryptonite #1 and #2 have identical masses, but the net force applied to #1 is 400 N and to #2 is 20 N. The acceleration

of #1 is larger

A quantity which is conserved in the collision of a car and a truck is

total momentum

You toss a ball straight up in the air. At the highest point, the ball's

velocity is zero and the acceleration is downward

A car is driven between two nearby towns at an average speed of 50 miles/hour. The magnitude of the average velocity of the car

will be the same as or less than the average speed

Two astronauts of equal mass are holding on to each other and moving at a speed of 30 m/s They push off of each other and one of the astronauts moves in the same direction as the two were initially moving but at 60 m/s. The velocity of the second astronaut is

zero