Laws Of Motion Test

Result

Laws Of Motion Test - 15

Score
-
out of -
Rank
-
out of -

TIME Taken - -

SHARING IS CARING

If our Website helped you a little, then kindly spread our voice using Social Networks. Spread our word to your readers, friends, teachers, students & all those close ones who deserve to know what you know now.

Weekly Quiz Competition

Question 1
1 / -0

A constant force acting on a body of mass 3 kg changes its speed from 2 m/s to 3.5 m/s in 10 second. If the direction of motion of the body remains unchanged, what is the magnitude and direction of the force?

A
0.45 N in the direction opposite to motion.

B
2.45 N in the direction of motion.

C
0.45 N in the direction of motion.

D
1.45 N in the direction opposite to motion.

Solution

Given : Mass, m = 3 kg;
Initial Velocity, u = 2m/s;
Final velocity, v = 3.5 m/s
Time taken, t = 10 seconds
v = u+at
3.5 = 2 +a x 10
F = ma = 3 x 0.15 = 0.45 N
Since the applied force increase the speed of the body, it acts along the direction of motion.
Question 2
1 / -0

The product of mass and velocity is known as

A
torque

B
impulse

C
momentum

D
acceleration

Solution

The product of velocity and mass is known as momentum which is a vector quantity.
Question 3
1 / -0

In cgs system the gravitational unit of force is gram weight (g wt).Then 1g wt (or g f) =_______ dyne.

A
980 dyne

B
9.8 N

C
980 N

D
9.8 dyne

Solution

For SI to CGS conversion,
1 Kg = 10³ g
1 m = 10² cm
=> In CGS System,
1 N (Kg.m/s²) = 105 dynes (g.cm/s²)
=> 1 g.wt = 9.8 m/s² x 10² cm / 1 s² x 10^-3 g x 10^-2 cm / 1 s x 10⁵ dynes
= 980 dynes (g.cm/s²)
Question 4
1 / -0

The dimensional formula of Plancks’s constant and angular momentum are

A
ML²T⁻¹ and MLT⁻¹

B
ML²T⁻¹ and ML²T⁻¹

C
MT⁻¹ and MLT⁻¹

D
ML²T⁻² and ML²T⁻¹

Solution

Planck's Constant (h) = 6.626176 x 10-34 m2 kg/s
So, Unit of planck constant= m² kg/s
Dimensions =M L² T ⁻¹ ________ (1)
Angular momentum l = mvr
Where, m-mass
v-velocity
r-radius
Dimensions of angular momentum = M L T ⁻¹ L = M L² T ⁻¹ _______________ (2)
From (1) and (2).
Planck's constant and angular momentum have the same dimensions.
Question 5
1 / -0

Which of the following quantity has the unit of newton-second?

A
Energy

B
Momentum

C
Torque

D
Acceleration

Solution

Net external force F = dp/dt, so using dimensional analysis, unit of momentum should be the same as unit of force times unit of time which is Newton second.
Question 6
1 / -0

If newton is the unit of force in MKS system then, in CGS system 1N= ______ dyne

A
10³

B
10⁴

C
10⁵

D
10⁶

Solution

1N = kg m /sec
1 dyne = gram cm/sec
Thus 1N in CGS system = 1000 gram 100 cm/sec
That is 1N = 100000 dyne
Question 7
1 / -0

Three forces act on an object of mass m = 2 kg. The acceleration of the object in m/s² is:

A

B

C

D

Solution

Force vector follows the principle of superposition which says all the force vectors can be vectorially added if applied on one point to get the net force vector. Hence we get
F = F₁ + F₂ + F₃
= (-2 + 3) i + (1 - 2) j
F = i - j = ma
Thus we get a = (i - j) /m
= (i - j) / 2
Question 8
1 / -0

Newton’s second law of motion relates

A
change of momentum and velocity

B
momentum and acceleration

C
Rate of change in force and momentum

D
Rate of change in momentum and external force

Solution

Newton's 2nd Law of motion states that rate of change of momentum is directly proportional to external force applied. Hence, it relates rate of change of momentum to external force applied.
Question 9
1 / -0

A cyclist of mass 30 kg exerts a force of 250 N to move his cycle. The acceleration is 4 ms⁻². The force of friction between the road and tyres will be

A
120 N

B
130 N

C
150N

D
115 N

Solution

F = ma so a= 250/30
a = 8.34
now the result is 4mt/secsqure so reduction is 4.34
so friction force will b 4.34 ×30
F is 130.2 n
Question 10
1 / -0

The time rate of change of momentum is called:

A
Acceleration

B
Impulse

C
force

D
Inertia

Solution

Time rate of change of angular momentum represents torque. Hence force is known as rate change of momentum. The rate of change of momentum is called force by Newton's second law of motion.