physics
unit 3: momentum
unit 3 test
(45 points)
name:
hour:
true/false (5 questions, 10 points)
1. momentum is defined as an objects mass times its velocity.
2. impulse is defined as the force exerted on an object times the time that the force lasts.
3. if the net external force acting on a system is zero, then the total momentum of the system is zero.
4. when two objects collide and stick together, the collision is said to be elastic.
5. perfectly elastic collisions between large objects are uncommon in the everyday world.
multiple-choice (13 questions, 26 points)
6. if the momentum of an object changes and its mass remains constant,
a. then it is accelerating (or decelerating).

Question

physics
unit 3: momentum
unit 3 test
(45 points)
name:
hour:
true/false (5 questions, 10 points)
1. momentum is defined as an objects mass times its velocity.
2. impulse is defined as the force exerted on an object times the time that the force lasts.
3. if the net external force acting on a system is zero, then the total momentum of the system is zero.
4. when two objects collide and stick together, the collision is said to be elastic.
5. perfectly elastic collisions between large objects are uncommon in the everyday world.
multiple-choice (13 questions, 26 points)
6. if the momentum of an object changes and its mass remains constant,
 a. then it is accelerating (or decelerating).

Accepted Answer

### True/False Questions:

#### 1. Momentum is defined as an object’s mass times its velocity.
# Brief Explanations:
The formula for momentum is $ p = mv $, where $ p $ is momentum, $ m $ is mass, and $ v $ is velocity. So this statement matches the definition.
# Answer:
True

#### 2. Impulse is defined as the force exerted on an object times the time that the force lasts.
# Brief Explanations:
The formula for impulse is $ J = F\Delta t $, where $ J $ is impulse, $ F $ is force, and $ \Delta t $ is the time interval. This matches the definition.
# Answer:
True

#### 3. If the net external force acting on a system is zero, then the total momentum of the system is zero.
# Brief Explanations:
The law of conservation of momentum states that if net external force ($ F_{net,ext} = 0 $), the total momentum of the system is **conserved** (remains constant), not necessarily zero. For example, a system with objects moving at constant velocity (non - zero momentum) with no net external force will have constant (non - zero) total momentum.
# Answer:
False

#### 4. When two objects collide and stick together, the collision is said to be elastic.
# Brief Explanations:
In an elastic collision, kinetic energy is conserved and objects do not stick together. When objects stick together after collision, it is a perfectly inelastic collision (kinetic energy is not conserved, and they move as one mass after collision).
# Answer:
False

#### 5. Perfectly elastic collisions between large objects are uncommon in the everyday world.
# Brief Explanations:
In real - world (everyday) collisions between large objects, there is usually some energy loss (due to sound, heat, deformation etc.). Perfectly elastic collisions (where kinetic energy is completely conserved) are rare in everyday scenarios for large objects.
# Answer:
True

### Multiple - choice Question 6 (partially visible, assuming we answer based on the visible part: "If the momentum of an object changes and its mass remains constant, a. then it is accelerating (or decelerating).")
# Brief Explanations:
Momentum $ p=mv $. If mass $ m $ is constant and momentum $ p $ changes, then velocity $ v $ must change (since $ p\propto v $ when $ m $ is constant). Acceleration is defined as the rate of change of velocity ($ a=\frac{\Delta v}{\Delta t} $). So a change in velocity means the object is accelerating (or decelerating, which is negative acceleration).
# Answer:
a. then it is accelerating (or decelerating)

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QUESTION IMAGE

Question

Explanation:

True/False Questions:

1. Momentum is defined as an object’s mass times its velocity.

Answer:

2. Impulse is defined as the force exerted on an object times the time that the force lasts.