Q1. A ball bounces higher at high altitudes than in plains. This is because
(a) The pressure on higher altitudes is lower than that in plains
(b) Downward pull due to gravity is less at higher altitudes
(c) The rarefied air offers less resistance to the ball
(d) You become more energetic at hills, so greater the force applied, higher goes the ball
Answer: (c) The rarefied air offers less resistance to the ball
Explanation: At high altitudes, the air is thinner (rarefied), resulting in less air resistance. This allows the ball to retain more of its kinetic energy, causing it to bounce higher compared to conditions in the denser air of the plains.
Q2. The escape velocity from the earth’s surface is about
(a) 30 km/sec
(b) 6 km/sec
(c) 11.2 km/sec
(d) 300 km/sec
Answer: (c) 11.2 km/sec
Explanation: Escape velocity is the minimum speed needed to break free from Earth’s gravitational pull, which is approximately 11.2 km/sec.
Q3. A person sitting in a bus experiences a jerk, when the bus stops all of a sudden. This is due to
(a) Law of inertia
(b) Newton’s third law of motion
(c) Einstein’s law of relativity
(d) None of these
(UPSC Prelims 1984)
Answer: (a) Law of inertia
Explanation: According to the law of inertia, a body in motion tends to remain in motion unless acted upon by an external force. When the bus stops suddenly, the passenger’s body continues moving forward, causing the jerk.