This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Forces of Nature”.
1. When we steer a bicycle round a bend with both our hands on the handlebars, we apply a ___________
a) Force
b) Torque
c) Couple
d) Energy
View Answer
Explanation: A pair of equal and opposite forces acting on a body along two different lines of action constitutes a couple. A Couple has a turning effect, but no resultant force acts on a body. When we steer a bicycle round a bend with both our hands on the handlebars, we apple a couple.
2. Couple cannot produce a translational motion.
a) True
b) False
View Answer
Explanation: A pair of equal and opposite forces acting on a body along two different lines of action constitutes a couple. A couple has a turning effect, but no resultant force acts on a body. Thus it cannot produce translational motion.
3. The areal velocity of a planet is constant. This is stated by ___________
a) Newton’s third law of motion
b) Kepler’s second law of planetary motion
c) Fourier’s law
d) Kirchhoff’s planetary law
View Answer
Explanation: A planet revolves around the sun under the influence of a gravitational force which acts towards the sun. This means that the areal velocity of a planet is constant. The is Kepler’s second law of planetary motion which states that the line joining the planet to the sun sweeps out equal areas in equal intervals of time.
4. The internal torque on the system due to internal force is ___________
a) Increasing
b) Decreasing
c) Constant
d) Zero
View Answer
Explanation: According to Newton’s third law, the internal torque on the system due to internal forces is zero because the forces between any two particles are equal and opposite and directed along the line joining the two particles. Hence the total torque is due to external forces only.
5. Which of the following can execute both translational and rotational motion under the influence of the external field?
a) Rigid body
b) Ideal body
c) Rotating body
d) A body which is stationary
View Answer
Explanation: A rigid body is one for which the distance between different particles does not change, even though they move. Under the influence of an external force, a rigid body can execute rotational and translational motion.
6. For a body in equilibrium, the linear acceleration of its centre of mass would be zero and also the angular acceleration of the rigid body about any axis would be zero.
a) True
b) False
View Answer
Explanation: A rigid body is in equilibrium if both the linear and angular momentum of the rigid body remains constant with time. Hence for a body on equilibrium, the linear acceleration of its centre of mass would be zero and also the angular acceleration of the rigid body about any axis would be zero.
7. A spring 40mm ling is stretched by the application of force. If 10N force is required to stretch the spring through 1mm, then the work done in stretching the spring through 40mm is?
a) 23J
b) 68J
c) 84J
d) 8J
View Answer
Explanation: Spring constant, k = F/x = 10N/1mm = 10N/(10-3 m)= 104 N/m
Work done in stretching the spring through 40m,
W = 1/2 kx2=1/2×104×(40×10-3)2 = 8J.
8. Two bodies w of masses m and 4m are moving with equal kinetic energies. What is the ratio of their linear momenta?
a) 1:2
b) 1:1
c) 4:1
d) 1:4
View Answer
Explanation: p = √2mE
For same kinetic energy, p1/p2 = √(m1/m2) = √(m/4m)=1:2.
9. Water falls from a height of 60m at the rate of 15kg.s to operate a turbine. The losses due to friction forces are 10% of energy. How much power is generated by the turbine? g=m/s2
a) 7kW
b) 10.2kW
c) 12.3kW
d) 8.1kW
View Answer
Explanation: P = W/t=mgh/t=(15×10×60)/1 = 9000W = 9kW
Loss=10%
Useful power=90% of 9kW = (90×9)/100=8.1kW.
10. A shell explodes into four unequal parts. Which one of the following is conserved?
a) Potential energy
b) Kinetic energy
c) Momentum
d) Both potential and kinetic energy
View Answer
Explanation: In the absence of external force, linear momentum is conserved. If a shell explodes into four equal parts, momentum is conserved.
Sanfoundry Global Education & Learning Series – Engineering Physics.
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