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block

An object has a velocity toward the south. If a force directed toward the south acts on the object, it will initially cause the kinetic energy of the object to ____.

Select the correct answer(s).  

(0/0)

---

remain the same

increase

decrease

none

A 3-kg toy car with a speed of 6 m/s collides head-on with a 2-kg car traveling in the opposite direction with a speed of 4 m/s. If the cars are locked together after the collision with a speed of 2 m/s, how much kinetic energy is lost?

Select the correct answer(s).  

(0/0)

---

28J

60J

70J

10J

none

Two objects have different masses but the same momenta. If you stop them with the same retarding force, which one will stop in the shorter distance?

Select the correct answer(s).  

(0/0)

---

Both stop in the same distance

the heavier one

the lighter one

none

Kinetic energy is defined to be one-half the

Select the correct answer(s).  

(0/0)

---

weight times the speed squared.

mass times the speed

mass times the speed squared.

mass times the acceleration.

none

If a sports car with a mass of 1000 kg travels down the road with a speed of 20 m/s, its kinetic energy is 200,000

Select the correct answer(s).  

(0/0)

---

kg/(m/s)2

kg·m2/s2

kg·m/s

kg·s2/m2

none

Under what conditions is the kinetic energy conserved in a collision?

Select the correct answer(s).  

(0/0)

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When there is no net outside force.

When there is no friction.

When the collision is totally elastic.

It is always conserved.

none

Under what conditions is energy conserved?

Select the correct answer(s).  

(0/0)

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When the system is closed to the flow of matter and energy.

When the system is closed to the flow of matter.

When the system is closed to the flow of energy.

Never

none

A sports car with a mass of 1000 kg travels down the road with a speed of 20 m/s. Which is larger, its momentum or its kinetic energy?

Select the correct answer(s).  

(0/0)

---

kinetic energy

The two cannot be compared.

momentum

They are equal.

none

You have been asked to analyze a collision at a traffic intersection. You would be better off

Select the correct answer(s).  

(0/0)

---

using conservation of kinetic energy, because while momentum was conserved, it is difficult to make the equation for momentum conservation work out

using conservation of momentum, because kinetic energy was probably not conserved during the collision

using conservation of kinetic energy, because momentum was probably not conserved during the collision

using conservation of momentum, because while kinetic energy was conserved, it is difficult to make the equation for kinetic energy conservation work out

none

When a star undergoes a supernova explosion, the total energy of the universe

Select the correct answer(s).  

(0/0)

---

decreases.

does not change.

increases.

none

Which has the greater kinetic energy, an 18-wheeler parked at the curb or a Volkswagen rolling down a hill?

Select the correct answer(s).  

(0/0)

---

Volkswagen

18-wheeler

The kinetic energies are equal

none

In physics, work is defined as the product of the

Select the correct answer(s).  

(0/0)

---

net force and the distance traveled.

net force parallel to the motion and the distance traveled.

applied force and the distance traveled.

net force parallel to the motion and the time it is applied

none

Assume that a red car has a mass of 1000 kg and a white car has a mass of 2000 kg. If both cars are traveling at the same velocity,

Select the correct answer(s).  

(0/0)

---

the white car's kinetic energy is twice as big.

their kinetic energies are equal.

the red car's kinetic energy is twice as big

their momenta are equal.

none

What is the kinetic energy of an 80-kg sprinter running at 9 m/s?

Select the correct answer(s).  

(0/0)

---

360J

720J

6480 J

3240 J

none

Assume that two cars have the same kinetic energy, but that the red car has twice the mass of the blue car. We then know that the speed of the red car is ____ as the blue car

Select the correct answer(s).  

(0/0)

---

none of these

one-half as much

twice as much

one-fourth as much

four times as much