Question

part 1: true or fall (10 points)
true or false
(t or f)
objects with a higher mass will always have higher momentum than objects with smaller mass.
momentum is conserved for both elastic and inelastic collisions.
momentum of an object strongly depends on the objects mass and how fast it moves.
in an open system, kinetic energy is conserved due to the conservation of momentum.
in reality, there is no collision that is perfectly inelastic or completely elastic.
higher mass objects will need more force to stop compared to smaller objects if both of them are moving at the same velocity.
the unit for momentum can be: g.m/s/s or kg.kh/h.
momentum of a stationary object will always be zero.
one example of elastic collision is gum sticking on the wall after being thrown.
one example of inelastic collision is bumper cars bouncing off each o

Explanation:

1. Objects with a higher mass will ALWAYS have higher momentum than objects with smaller mass.

Momentum \( p = mv \). If a small - mass object has a very high velocity, its momentum can be larger than a high - mass object with a low velocity. For example, a bullet (\(m = 0.01\space kg\), \(v= 500\space m/s\), \(p = 5\space kg\cdot m/s\)) and a truck (\(m = 1000\space kg\), \(v = 0.001\space m/s\), \(p=1\space kg\cdot m/s\)).

2. Momentum is conserved for both elastic and inelastic collisions.

According to the law of conservation of momentum, in the absence of external forces (\(F_{ext}=0\)), \(m_1u_1 + m_2u_2=m_1v_1 + m_2v_2\) for both elastic (\(KE\) conserved) and inelastic (\(KE\) not conserved) collisions.

3. Momentum of an object strongly depends on the object's mass and how fast it moves.

Since \(p = mv\), where \(m\) is mass and \(v\) is velocity.

4. In an open system, kinetic energy is conserved due to the conservation of momentum.

In an open system (\(F_{ext}
eq0\)), momentum is not conserved (\(\Delta p=\sum F_{ext}\Delta t\)) and kinetic energy is also not necessarily conserved. Kinetic energy conservation is a separate concept from momentum conservation (except in special cases like elastic collisions in isolated systems).

5. In reality, there is no collision that is perfectly inelastic or completely elastic.

In real - world collisions, there is always some energy loss (due to factors like sound, heat, deformation) for what we approximate as inelastic collisions and also no collision can conserve 100% of kinetic energy (due to non - ideal conditions) for what we approximate as elastic collisions.

6. Higher mass objects will need more force to stop compared to smaller objects if both of them are moving at the same velocity.

Using \(F=\frac{\Delta p}{\Delta t}=\frac{m\Delta v}{\Delta t}\). If \(\Delta v\) (from \(v\) to \(0\)) and \(\Delta t\) (stopping time) are the same, a larger \(m\) (higher mass) requires a larger \(F\).

7. The unit for momentum can be: [g.m/s/s] or [Kg.kh/h].

The unit of momentum is \(kg\cdot m/s\). \(g\cdot m/s/s=\frac{g\cdot m}{s^{2}}\) (unit of force if we consider \(F = ma\) and \(a=\frac{m}{s^{2}}\), \(g = 0.001\space kg\)) and \(kg\cdot km/h=\frac{kg\cdot1000m}{3600s}=\frac{5}{18}kg\cdot m/s\) (incorrect unit for momentum as the standard unit is \(kg\cdot m/s\)).

8. Momentum of a stationary object will ALWAYS be zero.

Since \(v = 0\) for a stationary object and \(p=mv\), so \(p = 0\).

9. One example of elastic collision is gum sticking on the wall after being thrown.

When gum sticks to the wall, it is a perfectly inelastic collision (objects stick together) and \(KE\) is not conserved (most of the \(KE\) is lost as heat, sound, and deformation energy).

10. One example of inelastic collision is bumper cars bouncing off each other.

Bumper - car collisions are approximately elastic (they bounce off and \(KE\) is approximately conserved). A better example of inelastic collision is two cars colliding and moving together after the collision.

Answer:

1. F
2. T
3. T
4. F
5. T
6. T
7. F
8. T
9. F
10. F