Physics Study guide

A 20-kg object sitting at rest is struck elastically in a head-on collision with a 10-kg object initially moving at +3.0 m/s. Find the final velocity of the 20-kg object after the collision.

+2.0 m/s

Two billiard balls have velocities of 2.0 m/s and 1.0 m/s when they meet in an elastic head on collision. What is the final velocity of the first ball after collision?

-1.0 m/s

Two identical 7-kg bowling balls roll toward each other. The one on the left is moving at +4 m/s while the one on the right is moving at 4 m/s. What is the velocity of each ball after they collide elastically?

-4 m/s, +4 m/s

A 20-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. What is the change in the kinetic energy of the bullet-block system as a result of the collision assuming the block is free to move?

-9.7 kJ

A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s. As a result of the collision, the first ball moves at 50.0 cm/s, and the second ball stops. What is the change in kinetic energy of the system as a result of the collision?

0

Two skaters, both of mass 75 kg, are on skates on a frictionless ice pond. One skater throws a 0.3-kg ball at 5 m/s to his friend, who catches it and throws it back at 5 m/s. When the first skater has caught the returned ball, what is the velocity of each of the two skaters?

0.04 m/s, moving apart

A 20-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. What is the kinetic energy of the block that results from the collision if the block had not been moving prior to the collision and was free to move?

0.16 kJ

A 75-kg swimmer dives horizontally off a 500-kg raft. If the diver's speed immediately after leaving the raft is 4 m/s, what is the corresponding raft speed?

0.6 m/s

A 1 000-kg experimental rocket sled at rest on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." The rocket moves at 150 m/s after the burn. What average force is experienced by the rocket during the burn?

0.75 x 104 N

A model car is propelled by a cylinder of carbon dioxide gas. The cylinder emits gas at a rate of 4.5 g/s with an exit speed of 80.0 m/s. The car has a mass of 400 g, including the CO2 cylinder. Starting from rest, what is the car's initial acceleration?

0.90 m/s2

A cannon of mass 1 500 kg fires a 10-kg shell with a velocity of 200 m/s at an angle of 45 above the horizontal. Find the recoil velocity of the cannon across the level ground.

0.94 m/s

A 2 500 kg truck moving at 10.00 m/s strikes a car waiting at a traffic light, hooking bumpers. The two continue to move together at 7.00 m/s. What was the mass of the struck car?

1 070 kg

a 75-kg swimmer dives horizontally off a 500-kg raft. the diver's speed immediately after leaving the raft is 4.0 m/s. a micro-sensor system attatched to the edge of the raft measures the time interval during which the diver applies an impulse to the raft just prior to leaving the raft surface. if the time interval is read as 0.20 s, what is the magnitude of the average horizaontal force by diver on the raft?

1 500 N

a uranium nucleus (mass 238 units) at rest decays into a helium nucleus (mass 4.0 units) and a thorium nucleus (mass 234 units). if the speed of the helium nucleus is 6.0 x 10^5 m/s, what is the speed of the thorium nucleus?

1.0 x 10^4 m/s

Alex throws a 0.15-kg rubber ball down onto the floor. the ball's speed just before impact is 6.5 m/s, and just after is 3.5 m/s. what is the change in the magnitude of the ball's momentum?

1.5 kgm/s

A 1 000-kg experimental rocket sled on level frictionless rails is loaded with 50 kg of propellant. It exhausts the propellant in a 20-s "burn." If the rocket, initially at rest, moves at 150 m/s after the burn, what impulse is experienced by the rocket sled?

1.5 x 105 kgm/s

A 1.00-kg duck is flying overhead at 1.50 m/s when a hunter fires straight up. The 0.010 0-kg bullet is moving 100 m/s when it hits the duck and stays lodged in the duck's body. What is the speed of the duck and bullet immediately after the hit?

1.78 m/s

Popeye, of mass 70 kg, has just downed a can of spinach. He accelerates quickly and stops Bluto, of mass 700 kg (Bluto is very dense), who is charging in at 10 m/s. What was Popeye's speed?

100 m/s

a miniature spring-loaded, radio-controlled gun is mounted on an air puck. the gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. with the system initially at rest, the radio controlled trigger releases the bullet causing the puck and empty gun to move with a speed of 0.500 m/s. what is the bullet's speed?

12.0 m/s

A 20-g bullet moving at 1 000 m/s is fired through a one-kg block of wood emerging at a speed of 100 m/s. If the block had been originally at rest and is free to move, what is its resulting speed?

18 m/s

A rocket of total mass M and with burnout mass 0.20 M attains a speed of 3 200 m/s after starting from rest in deep space. What is the exhaust velocity of the rocket?

2 000 m/s

A 90 kg halfback running north with a speed of 10 m/s is tackled by a 120 kg opponent running south at 4 m/s. The collision is perfectly inelastic. Compute the velocity of the two players just after the tackle.

2 m/s north

A 0.12-kg ball is moving at 6 m/s when it is hit by a bat, causing it to reverse direction and have a speed of 14 m/s. What is the change in the magnitude of the momentum of the ball?

2.4 kgm/s

lonnie pitches a baseball of mass 0.20 kg. the ball arives at home plate with a speed of 40 m/s and is batted straight back to lonnie with a return speed of 60 m/s. if the bat is in contact with the ball for 0.050 s, what is the impulse experienced by the ball?

20 N * s

Jerome pitches a baseball of mass 0.20 kg. The ball arrives at home plate with a speed of 40 m/s and is batted straight back to Jerome with a return speed of 60 m/s. What is the magnitude of change in the ball's momentum?

20 kgm/s

A railroad freight car, mass 15 000 kg, is allowed to coast along a level track at a speed of 2.0 m/s. It collides and couples with a 50 000-kg loaded second car, initially at rest and with brakes released. What percentage of the initial kinetic energy of the 15 000-kg car is preserved in the two-coupled cars after collision?

23%

A helicopter stays aloft by pushing large quantities of air downward every second. What mass of air must be pushed downward at 40.0 m/s every second to keep a 1 000-kg helicopter aloft?

245 kg

Mitch throws a 100 g lump of clay at a 500-g target, which is at rest on a horizontal surface. After impact, the target, including the attached clay, slides 2.1 m before stopping. If the coefficient of friction is µ = 0.50, find the speed of the clay before impact.

27 m/s

A neutron in a nuclear reactor makes an elastic head on collision with a carbon atom initially at rest. (The mass of the carbon atom is 12 times that of the neutron.) What fraction of the neutron's kinetic energy is transferred to the carbon atom?

28.4%

During a snowball fight two balls with masses of 0.4 and 0.6 kg, respectively, are thrown in such a manner that they meet head on and combine to form a single mass. The magnitude of initial velocity for each is 15 m/s. What is the speed of the 1.0-kg mass immediately after collision?

3 m/s

At liftoff, the engines of the Saturn V rocket consumed 13 000 kg/s of fuel and exhausted the combustion products at 2 900 m/s. What was the total upward force (thrust) provided by the engines?

3.77 x 107 N

A 0.10-kg object moving initially with a velocity of +0.20 m/s makes an elastic head on collision with a 0.15-kg object initially at rest. What percentage of the original kinetic energy is retained by the 0.10-kg object?

4%

A machine gun is attached to a railroad flatcar that rolls with negligible friction. If the railroad car has a mass of 6.25 104 kg, how many bullets of mass 25 g would have to be fired at 250 m/s off the back to give the railroad car a forward velocity of 0.5 m/s?

5 000

Ann the Astronaut weighs 60 kg. She is space walking outside the space shuttle and pushes a 350-kg satellite away from the shuttle at 0.90 m/s. What speed does this give Ann as she moves toward the shuttle?

5.3 m/s

A 7.0 kg bowling ball strikes a 2.0 kg pin. The pin flies forward with a velocity of 6.0 m/s; the ball continues forward at 4.0 m/s. What was the original velocity of the ball?

5.7 m/s

Alex throws a 0.15-kg rubber ball down onto the floor. The ball's speed just before impact is 6.5 m/s, and just after is 3.5 m/s. If the ball is in contact with the floor for 0.025 s, what is the magnitude of the average force applied by the floor on the ball?

60 N

a crane drops a 0.30-kg steel ball onto a steel plate. the ball's speeds just before impact and after are 4.5 m/s and 4.2 m/s, respectively. if the ball is in contact with the plate for 0.30 s, what is the magnitude of the average force that the ball exerts on the plate during impact?

87 N

A miniature, spring-loaded, radio-controlled gun is mounted on an air puck. The gun's bullet has a mass of 5.00 g, and the gun and puck have a combined mass of 120 g. With the system initially at rest, the radio-controlled trigger releases the bullet, causing the puck and empty gun to move with a speed of 0.500 m/s. Of the total kinetic energy of the gun puck bullet system, what percentage is in the bullet?

96%

two masses m1 and m2 with m1<m2, have moments with equal magnitudes. how do their kinetic energies compare?

KE1 > KE2

the dimentional equivalent of the quantity impulse in terms of the fundamental quantities is which of the following?

MLT^ -1

Two masses collide and stick together. Before the collision one of the masses was at rest. Is there a situation in which the kinetic energy is conserved in such a collision?

No, kinetic energy is always lost is such a collision.

An object of mass m moving at speed v0 strikes and object of mass 2m which had been at rest. The first object bounces backward along its initial path at speed v0. Is this collision elastic, and if not, what is the change in kinetic energy of the system?

The kinetic energy increases by mv2.

three satelites are launched into space connected together. once in deep space, an explosive charge seperates the three satellites and they move apart. the satellites each have different masses with m1<m2<m3. which of the following statements is always true?

although one or more of the above statements could be true in special cases, they are not always true

A billiard ball is moving in the x-direction at 30.0 cm/s and strikes another billiard ball moving in the y-direction at 40.0 cm/s. As a result of the collision, the first ball moves at 50.0 cm/s, and the second ball stops. In what final direction does the first ball move?

at an angle of 53.1o ccw from the x-direction

A billiard ball collides in an elastic head on collision with a second stationary identical ball. After the collision which of the following conditions applies to the first ball?

comes to rest

A 5-kg object is moving to the right at 4 m/s and collides with a 4-kg object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:

has no kinatic energy

a valid unit for momentum is which of the following?

kgm/s

the units of impulse are equivalent to:

kgm/s

A 5-kg object is moving to the right at 4 m/s and collides with another object moving to the left at 5 m/s. The objects collide and stick together. After the collision, the combined object:

less kinetic energy than the system had before the collision.

the impulse experienced by a body is equivalent to its change in:

momentum

two body collision is not head on, then we may always assume that:

momentum is conserved

object 1 has twice the mass of object 2. both objects have the same kinetic energy. which of the following statements is true?

object 1 has a momentum of greater magnitude than object 2

A model rocket sits on the launch pad until its fuel is ignited, blasting the rocket upward. During the short time of blast off, as the ignited fuel goes down, the rocket goes up because:

of none of the above reasons.

object 1 has twice the mass of object 2. each object has the same magnitude and momentum. which of the following statements is true?

one object has twice the kinetic energy of the other

a lump of clay is thrown at a wall. a rubber ball of identical mass is thrown withthe same speed toward the same wall. which statement is true?

the ball experiences a greater change in momentum than the clay.

Neglecting gravity, doubling the exhaust velocity from a single stage rocket initially at rest changes the final kinetic energy of the burnout stage by what factor? Assume all other variables, such as the mass of the rocket and the mass of the fuel, do not change.

the final velocity doubles

Two objects, one less massive than the other, collide elastically and bounce back after the collision. If the two originally had velocities that were equal in size but opposite in direction, then which one will be moving faster after the collision?

the less massive one

a 70-kg man is standingin a 20-kg boat. the man steps to the right thinking he is stepping out onto the dock. however, the following will actuallly happen (ignore the friction of the water or air on the boat or the man):

the man only moves a short distance to the right while the boat moves a larger distance to the left

A tennis ball is held above and in contact with a basketball, and then both are simultaneously dropped. The tennis ball bounces off the basketball at a fairly high speed. This is because:

the massive basketball transfers momentum to the lighter tennis ball.

In a partially elastic collision between two objects with unequal mass:

the momentum of one will increase by the amount that the momentum of the other decreases.

when a collision is perfectly inelastic, then:

the participants stick together

A billiard ball collides in an elastic head on collision with a second identical ball. What is the kinetic energy of the system after the collision compared to that before collision?

the same as

If a glass of water is on a table with a piece of paper under it, it is relatively easy to pull the paper out without disturbing the glass very much if the pull is done very quickly. This is because, with a quick pull:

the time for the pull will be less.

Kaitlin uses a bat to hit a thrown baseball. She knocks the ball back in the direction from which it came in a partially inelastic collision. The bat, which is heavier than the baseball, continues to move in the same direction after the hit as Kaitlin "follows through." Is the ball moving faster before or after it was hit?

there is insufficient information to answer this problem

Two masses m1 and m2, with m1 = 3 m2, undergo a head-on elastic collision. If the particles were approaching with speed v before the collision, with what speed are they moving apart after collision?

v