1.
Two objects stick together and move with a common velocity after colliding. Identify the type of collision.
Correct Answer
D. Perfectly Inelastic
Explanation
In a perfectly inelastic collision, two objects stick together and move with a common velocity after colliding. This means that the kinetic energy is not conserved in the collision, as some of it is lost and converted into other forms of energy, such as heat or deformation. The objects become permanently deformed or stick together, resulting in a loss of kinetic energy.
2.
Two billiard balls collide. Identify the type of collision.
Correct Answer
A. Elastic
Explanation
The type of collision between the billiard balls is elastic. In an elastic collision, the kinetic energy is conserved, and the objects bounce off each other without any loss of energy. This means that after the collision, the billiard balls will continue to move with the same total kinetic energy as before the collision.
3.
Two balls of dough collide and stick together. Identify the type of collision.
Correct Answer
D. Perfectly inelastic
Explanation
In a perfectly inelastic collision, two objects collide and stick together, resulting in a loss of kinetic energy. In this case, the two balls of dough collide and stick together, indicating that the collision is perfectly inelastic.
4.
Two cars collide, lock bumpers, and move together after the collision.
Correct Answer
D. Perfectly inelastic
Explanation
When two cars collide and lock bumpers, and then move together after the collision, it indicates a perfectly inelastic collision. In a perfectly inelastic collision, the two objects stick together and move as one after the collision. This happens when the objects deform and lose some of their kinetic energy during the collision. In this case, the cars collide, and their bumpers lock, causing them to move together after the collision, indicating a perfectly inelastic collision.
5.
A tennis ball is dropped from 1.0 m, bounces off the ground, and rises to 0.85 m. What kind of collision occurred between the ball and the ground?
Correct Answer
B. Inelastic
Explanation
The collision between the tennis ball and the ground is considered inelastic because the ball does not regain its original height after bouncing off the ground. In an inelastic collision, some of the kinetic energy is lost as heat or sound, and the objects involved stick together or deform. Since the ball rises to a lower height than its initial position, it indicates that some of the energy was not conserved during the collision, making it an inelastic collision.
6.
In what kind of collision is kinetic energy always conserved?
Correct Answer
C. Perfectly elastic
Explanation
A perfectly elastic collision is a type of collision where both momentum and kinetic energy are conserved. This means that the total kinetic energy of the system (the sum of the kinetic energies of all the objects involved) before the collision is equal to the total kinetic energy of the system after the collision. Perfectly elastic collisions are idealized scenarios, as most real-world collisions involve some conversion of kinetic energy into other forms of energy such as heat or sound, but they are useful for theoretical calculations and in situations where the energy losses are negligible.
7.
A helium atom collides with another helium atom in an elastic collision. Which of the following is true?
Correct Answer
A. Both momentum and kinetic energy are conserved.
Explanation
In an elastic collision, both momentum and kinetic energy are conserved. Momentum is a vector quantity that is conserved in collisions, meaning that the total momentum before the collision is equal to the total momentum after the collision. Kinetic energy is a scalar quantity that represents the energy of motion, and in an elastic collision, the total kinetic energy before the collision is equal to the total kinetic energy after the collision. Therefore, in the given scenario of a helium atom colliding with another helium atom in an elastic collision, both momentum and kinetic energy are conserved.
8.
Two playground balls collide in an inelastic collision. Which of the following is true?
Correct Answer
B. Momentum is conserved, but kinetic energy is not conserved.
Explanation
In an inelastic collision, the two playground balls stick together after colliding. This means that they move as one object after the collision. Momentum is conserved because the total momentum before the collision is equal to the total momentum after the collision. However, kinetic energy is not conserved because some of the initial kinetic energy is transformed into other forms of energy, such as heat or sound, during the collision.
9.
In an inelastic collision between two objects with unequal masses,
Correct Answer
D. The momentum of one object will increase by the amount that the momentum of the other object decreases.
Explanation
In an inelastic collision, the total momentum of the system is conserved. However, since the objects have unequal masses, the momentum transfer between the objects will cause the momentum of one object to increase by the amount that the momentum of the other object decreases. This is because the more massive object will transfer more momentum to the less massive object, resulting in an increase in its momentum. Therefore, the correct answer is that the momentum of one object will increase by the amount that the momentum of the other object decreases.
10.
A billiard ball collides with a stationary identical billiard ball in an elastic head-on collision. After the collision, which of the following is true of the first ball?
Correct Answer
C. It comes to rest.
Explanation
In an elastic head-on collision, the first billiard ball comes to rest after colliding with the stationary identical billiard ball. This is because in an elastic collision, both the momentum and kinetic energy are conserved. Since the second billiard ball is stationary, it has zero initial velocity and zero momentum. In order to conserve momentum, the first ball must also have zero momentum after the collision, meaning it comes to rest.
11.
A ship with a mass of 4.50 x 10^{7} kg and a velocity of 2.30 m/s to the north collides with another ship whose mass is 2.30 x 10^{7} kg. If the speed of the second ship is 3.40 m/s to the south, what is the change in the kinetic energy after the two ships undergo a perfectly inelastic collision?
Correct Answer
C. -2.47 x 10^8 J
Explanation
In a perfectly inelastic collision, the two objects stick together and move as one after the collision. The change in kinetic energy can be calculated using the equation ΔKE = KE_final - KE_initial. Initially, the total kinetic energy is the sum of the kinetic energies of the two ships, given by KE_initial = (1/2) * m1 * v1^2 + (1/2) * m2 * v2^2. After the collision, the total kinetic energy is given by KE_final = (1/2) * (m1 + m2) * v_final^2. Plugging in the given values, we can calculate the change in kinetic energy to be -2.47 x 10^8 J.
12.
A ball of clay with a mass of 55 g and a speed of 1.5 m/s collides with a 55 g ball of clay that is at rest. What is the kinetic energy after the inelastic collision?
Correct Answer
B. -0.03 J
13.
The hog-nosed bat is the smallest mammal on Earth: it is about the same size as a bumblebee and has an average mass of 2.0 g. Suppose a hog-nosed bat with this mass flies at 2.0 m/s when it detects a bug with a mass of 0.20 g flying directly toward it at 8.0 m/s. What is the velocity of the bug and the bat after the collision?
Correct Answer
D. 1.09 m/s
Explanation
The velocity of the bug and the bat after the collision is 1.09 m/s because the principle of conservation of momentum states that the total momentum before the collision is equal to the total momentum after the collision. Since the bug is flying directly toward the bat, their velocities will add up. The momentum of the bat before the collision is (2.0 g) * (2.0 m/s) = 4.0 g*m/s, and the momentum of the bug before the collision is (0.20 g) * (-8.0 m/s) = -1.6 g*m/s. The total momentum before the collision is 4.0 g*m/s - 1.6 g*m/s = 2.4 g*m/s. After the collision, the total momentum is still 2.4 g*m/s, so the velocity of the bug and the bat after the collision is 2.4 g*m/s / (2.2 g) = 1.09 m/s.
14.
The cheapest car ever commercially produced was the , which sold in 1922 in the United States for about $250. The car’s mass was only 111 kg. Suppose two of these cars are used in a stunt crash for an action film. If one car’s initial velocity is 9.00 m/s to the right and the other car’s velocity is 5.00 m/s to the left, what is the velocity of the cars after the collision?
Correct Answer
C. 2 m/s
Explanation
After the collision, the cars will have a combined velocity that is the sum of their initial velocities. Since one car is moving to the right and the other car is moving to the left, their velocities have opposite signs. By adding the magnitudes of their velocities and giving the sum the sign of the larger velocity, we find that the cars will have a velocity of 2 m/s to the right after the collision.