The momentum of a system is conserved when A) net work is zero B) when the syste

Question

The momentum of a system is conserved when A) net work is zero B) when the system is isolated C) only during collisions. D) when the kinetic energy is conserved. As the spring stretches farther and farther A) the spring force increases as the spring stretches. B) the spring force decreases as the spring stretches. C) the spring force is constant as the spring stretches. D) not enough information. A simple pendulum is made using a string and a mass. Where will the simple pendulum have the longer period? A) on Earth B) on the Moon C) same period on both When an object oscillates many times before stopping, the oscillation is said to be A) driven B) critically damped C) overdamped D) underdamped Two objects with mass 2.0 kg and 5.0 kg are at rest. The same impulse is applied to both objects. The object with the larger velocity after the impulse is applied is A) The 2.0 kg mass. B) The 5.0 kg mass. C) Have the same velocity. D) Need to know the time the impulse acts. The center of mass between Jupiter and one if its moons, Europa is A) closer to the center of Europa and between Jupiter and Europa B) closer to the center of Jupiter and on the opposite side of Jupiter from Europa. C) closer to the center of Europa and on the opposite side of Europa from Jupiter D) closer to the center of Jupiter and between Jupiter and Europa. A mass is oscillating in simple harmonic motion. The points at which the maximum speed and the maximum acceleration occur are A) at equilibrium for both speed and acceleration. B) at equilibrium for acceleration and at amplitude for speed. C) at the amplitude for both speed and acceleration. D) at equilibrium for speed and at amplitude for acceleration. Internal forces are forces that A) are exerted on an object on itself. B) are exerted by objects not in the system on other objects not in the system. C) are exerted by objects in the system on objects not in the system. D) are exerted by objects in the system on other objects in the system.

Explanation / Answer

Q1.

momentum of a system is conserved, when there is no external force involved.

i.e when external force on the system =0, momentum is conserved.

zero external force means the system is isolated.

hence option B is correct.

Q2. from hooke's law, spring force is directly proportional to expansion or contraction.

hence as spring stretches, the spring force will increase.

hence option A is correct.

Q3.

for a pendulum made of a string a mass, the time period is given by

2*pi*sqrt(L/g)

where L is length of the string and g is acceleration due to gravity.

as acceleration due to gravity on moon is lesser than earth,

time period will be longer on the moon.

hence option B is correct.

Q4.

when object oscillates many times before stopping , the oscillation is said to be underdamped

it is a basic characteristics of underdamped oscillation.

hence option D is correct.

Q5.

impulse=mass*change in velocity

==>change in velocity=impulse/mass

larger the mass , smaller is change in velocity.

and smaller is the mass, larger is the change in velocity.

hence the object with larger velocity after the impulse is applied is the 2 kg mass.

hence option A is correct.

Q6.

let the two masses are M and m with M>m .

let origin be at the center of M and distance of center of m from center of M is d.

distance of center of mass from origin=(M*0+m*d)/(M+m)

=m*d/(M+m)

as M>m

==>M+m >m+m=2*m

==>m/(M+m) <1/2

==>m*d/(m+M) < d/2

hence center of mass is at a distance lesser than d/2 from center of M and hence closer to center of the bigger object.

so option D is correct.

Q7.

simple harmonic motion equation can be written as

y=A*sin(w*t)

where y =displacement

A=amplitude

w=angular frequency

then speed=dy/dt=A*w*cos(w*t)

acceleration=-w^2*A*sin(w*t)

equlibrium will occur when y=0 =>sin(w*t)=0

maximum speed occurs when cos(w*t)=1 ==>sin(w*t)=0==>at equilibrium

maximum acceleration will occur, when sin(w*t)=1==>y=A=amplitude

hence option D is correct.

Q8.

option D is correct.

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