This set of Engineering Physics Multiple Choice Questions & Answers (MCQs) focuses on “Forces”.
1. Force is a polar vector.
Explanation: Force is a polar vector because it has a point of application. It is a push or a pull that tends to change the state of rest or of uniform motion of a body.
2. A body is moving along a straight path. What will happen to the body in the absence of an external field?
a) It will stop
b) It will move with the same speed in a different path
c) It will move with the same speed along the same straight path
d) It will move with a reduced speed along the same path
Explanation: Galileo stated that on a horizontal plane an object should move with a constant velocity in a straight line path. Therefore a body moving along a straight path will continue to move in the same direction with the same speed even in the absence of external forces.
3. A person is standing in a bus. When the bus starts moving forward suddenly
a) The person moves forward
b) The person remains stationary
c) The person is unaffected
d) The person moves backward
Explanation: A person standing in a bus moves backward when the bus moves forward. When the bus moves forward, the lower part of his body begins to move along with the bus while the upper part of his body continues to remain at rest due to inertia. That is why a person falls backward when the bus starts.
4. When a moving bus suddenly stops, a person sitting
a) Stands up
b) Falls forward
c) Falls backward
d) Is unaffected
Explanation: As the bus stops, the lower part of the person’s body comes to rest along with the bus while the upper part of his body continues to remain in motion due to inertia and therefore the person falls forward.
5. If a body has more mass, it had more inertia.
Explanation: Mass of the body is the measure of its inertia. If a body has more mass, it is more difficult to change its state of rest or of uniform motion.
6. Which of the following is also known as the law of inertia?
a) Newton’s second law of motion
b) Newton’s third law of motion
c) Aristotelian law of motion
d) Newton’s first law of motion
Explanation: According to Newton’s first law of motion, every body continues in its state of rest or uniform motion unless an external force acts upon it. This inability of a body to change its state of rest or of uniform motion along a straight path is called inertia of a body. Hence the first law of motion is also called a law of inertia.
7. When we shake the branch of a tree, its fruits and dry leaves fall down. This is an example for
a) Inertia of motion
b) Inertia of rest
c) Inertia of direction
d) Newton’s third law of motion
Explanation: On shaking, the branch comes into motion while the dry fruits and leaves tend to remain at rest, inertia at rest, and so get separated. Thus the falling of leaves and fruits when the branch is shaken is an example of inertia of rest.
8. A ball thrown upward in a moving train does not come back into the thrower’s hand.
Explanation: The ball acquires the horizontal velocity of the train and maintains it during its upward and downward motion. In this period the ball covers the same horizontal distance as the train, so it comes back into the thrower’s hands.
9. A dog is chasing a hare and the hare runs in a zigzag path. What happens?
a) The dig becomes confused
b) The dog catches the hare easily
c) It becomes difficult for the dog to catch the hare
d) The hare dies
Explanation: When the hare runs in a zigzag path, it becomes difficult for the dog to catch the hare. This is because the dog has more mass and hence has more inertia of direction than that of the hare.
10. The driver of a car suddenly sees a broad wall in front of him. He should
a) Brake sharply
b) Turn sharply
c) Keep going
d) Jump out of the car
Explanation: Suppose FBis the force required in applying brakes to stop the truck in distance d, then
FB × d = 1/2mv2
Suppose FT is the force required in taking a turn of radius d then,
FT = 2FB
Clearly, it is better to apply brakes than to take a circular turn.
Sanfoundry Global Education & Learning Series – Engineering Physics.
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