Question

S/13495/quizzes/27508/take D Question 1 10 pts Which among the following statements is CORRECT? An object's weight is the same whether it is on the Moon, on the Earth, or on any other planet If the net force on an object is zero, it must be motionless or moving with a constant velocity. If gravity were to drop to zero the mass of an object would also become zero. An object's mass is different on the Moon than on the Earth. Question 2 10 pts A 10 kg block starts from rest at the top of a rough incline of angle 30°and slides 4.0m down in 20 seconds. The coefficient of kinetic friction between the block and the incline is given by 0.34 0.58 0.12 4.9

Answer 1

Question 1 :

If the net force on an object is zero, it must be motionless or moving with constant velocity.

we know that , according to Newton's second law

F_net = ma

Since F_net = 0

ma = 0

hence a = 0

as acceleration is zero, the velocity must be constant or zero.

Question 2:

NV lp mg sinzo V mg cosso

N = normal force

m = mass of the block = 10 kg

v_o = initial velocity of the block = 0 m/s

x = displacement = 4 m

t = time taken = 2 sec

a = acceleration

Using the kinematics equation

x = v_o t + (0.5) a t²

4 = (0) (2) + (0.5) a (2)²

a = 2 m/s²  

f = frictional force

from the force diagram, force equation parallel to incline surface is given as

mg Sin30 - f = ma

(10 x 9.8) Sin30 - f = 10 (2)

f = 29 N

from the force diagram, force equation perpendicular to incline surface is given as

N = mg Cos30

N = (10 x 9.8) Cos30

N = 84.87 N

Coefficient of friction is given as

$\mu$ = f/N

$\mu$ = 29/84.87

$\mu$ = 0.34