Question

8.1 linear momentum, force, and impulse

1. if an objects velocity is constant, what is its momentum proportional to?

a. its shape
b. its mass
c. its length
d. its breadth

1. if both mass and velocity of an object are constant, what can you tell about its impulse?

a. its impulse would be constant.
b. its impulse would be zero.
c. its impulse would be increasing.
d. its impulse would be decreasing.

1. when the momentum of an object increases with respect to time, what is true of the net force acting on it?

a. it is zero, because the net force is equal to the rate of change of the momentum.
b. it is zero, because the net force is equal to the product of the momentum and the time interval.
c. it is nonzero, because the net force is equal to the rate of change of the momentum.
d. it is nonzero, because the net force is equal to the product of the momentum and the time interval.

Explanation:

• Question 31: The formula for linear momentum is \(p = mv\) (where \(p\) is momentum, \(m\) is mass, and \(v\) is velocity). If \(v\) is constant, then \(p\propto m\) (momentum is proportional to mass).
• Question 32: Impulse \(J=\Delta p\) (change in momentum). Since \(p = mv\) and both \(m\) and \(v\) are constant, \(\Delta p=0\), so \(J = 0\).
• Question 33: According to Newton's second law in terms of momentum, \(F_{net}=\frac{\Delta p}{\Delta t}\). If \(p\) (momentum) is increasing with time (\(\Delta p

eq0\)), then \(F_{net}
eq0\) as \(F_{net}\) is the rate of change of momentum.

Answer:

• 31. B. Its mass
• 32. B. Its impulse would be zero
• 33. C. It is nonzero, because the net force is equal to the rate of change of the momentum