Question

True/False. Mark your answers to the left of each question.
a. Two solid spheres with the same diameter but different masses will
experience the same acceleration when dropped from the same height.
b. A load being lifted by a crane at a constant velocity has no net force acting
on it.
c. After a firecracker, initially at rest explodes, the total momentum of all of
the pieces is no longer zero.
d. Two solid spheres with different diameters but the same mass are rolled
down an incline. The sphere with the smaller diameter will accelerate
faster.
e. The work done by the net force on an object always causes a change in
objects speed.
f. In an inelastic collision momentum is not conserved.
g. An object in equilibrium has no net torque around any pivot point.
h. The period of a pendulum decreases if the mass of the pendulum
increases.
i. If all of the forces on a system at rest are internal forces, the center of
mass cannot change.
j. If the pressure of an ideal gas is doubled at constant temperature and
number of molecules, the volume of the gas must be halved.
k. The average velocity of molecules in an ideal gas is proportional to three
times the temperature.
l. An isolated system in thermal equilibrium has its maximum value of
entropy.

Answer 1

a] TRUE

since when dropped, Vi=0m/s, a=g=9.8 m/s²

Using the kinematic equation; h= Vi*t+1/2at^2

we get, h=1/2gt^2 , which is independent of mass

b] TRUE

At constant velocity, no acceleration, hence F_net= ma=0N

c] FALSE

here momentum is conserved ib both elastic and non-elastic collision

hence initially firce cracker at rest ,Pinital=0kg m/s , thereby Pfinal= Pinital= 0 kg m/s

d] TRUE

Moment of inertia of solid sphere,I=2/5 mr²

so with smaller radius[r] , I is smaller hence accelerate faster.

e] TRUE

There is a strong connection between work and energy, in a sense that when there is a net force doing work on an object, the object's kinetic energy will change by an amount equal to the work done

change in Ke= 1/2m[v_f²-v_i²]

f] FALSE

Both in elastic and inelastic collision momentum is conserved.

g] TRUE

Equilibrium means no external force, hence no net torque on it.

h] FALSE

Here period of the pendulum, T=2* pie* [l/g]^1/2,which doesn't depends on the mass of the pendulum

i]FALSE

The motion of centre of mass is solely controlled by the external forces acting on the various component of the system.

j] TRUE

since Pressure is inversely proportional to volume.

k]FALSE

The average velocity, V_avg=3/2KT

l] TRUE

For isolated systems, entropy never decreases.