if i were a milionarie
Basic Physics Content with Answers
1. In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. At the 10m position, half way up, the net force on the ball is
A. 2mg.
B. mg.
C. mg/2.
D. mg/4.
B is correct, as a vector diagram would show. Other choices show carelessness or confusion between force and speed, and what constant acceleration means.
2. When you drop a ball it accelerates downward at 9.8 m/s2. If you instead throw it downward, then its acceleration immediately after leaving your hand, assuming no air resistance, is
A. 9.8 m/s2.
B. more than 9.8 m/s2.
C. less than 9.8 m/s2.
D. Cannot say, unless the speed of throw is given.
A is correct. Choices B and D indicate confusion between speed and acceleration.
3. A heavy rock and a light rock in free fall (zero air resistance) have the same acceleration. The reason the heavy rock doesn’t have a greater acceleration is that the
A. force due to gravity is the same on each.
B. air resistance is always zero in free fall.
C. inertia of both rocks is the same.
D. ratio of force to mass is the same.
E. None of these.
D is correct. Choices A and C indicate confusion about Newton’s second law. Choice B, although a true statement, evades the reason, and is therefore not the best answer.
4. A cannonball is fired horizontally at 10 m/s from a cliff. Its speed one second after being fired is about
A. 10 m/s.
B. 14 m/s.
C. 16 m/s.
D. 20 m/s.
B is correct, as vector addition shows if a student knows that gain of vertical speed in 1 s is 10 m/s. Choice a gives the horizontal or vertical speed, but not the resultant speed. Choice C has no credibility, and choice D indicates scalar addition of two 10 m/s vectors.
5. Relative to the ground, an airplane gains speed when it encounters wind from behind, and loses speed when it encounters wind head on. When it encounters wind at a right angle to the direction it is pointing, its speed relative to the ground below
1. In the absence of air resistance, a ball of mass m is tossed upward to reach a height of 20 m. At the 10m position, half way up, the net force on the ball is
A. 2mg.
B. mg.
C. mg/2.
D. mg/4.
B is correct, as a vector diagram would show. Other choices show carelessness or confusion between force and speed, and what constant acceleration means.
2. When you drop a ball it accelerates downward at 9.8 m/s2. If you instead throw it downward, then its acceleration immediately after leaving your hand, assuming no air resistance, is
A. 9.8 m/s2.
B. more than 9.8 m/s2.
C. less than 9.8 m/s2.
D. Cannot say, unless the speed of throw is given.
A is correct. Choices B and D indicate confusion between speed and acceleration.
3. A heavy rock and a light rock in free fall (zero air resistance) have the same acceleration. The reason the heavy rock doesn’t have a greater acceleration is that the
A. force due to gravity is the same on each.
B. air resistance is always zero in free fall.
C. inertia of both rocks is the same.
D. ratio of force to mass is the same.
E. None of these.
D is correct. Choices A and C indicate confusion about Newton’s second law. Choice B, although a true statement, evades the reason, and is therefore not the best answer.
4. A cannonball is fired horizontally at 10 m/s from a cliff. Its speed one second after being fired is about
A. 10 m/s.
B. 14 m/s.
C. 16 m/s.
D. 20 m/s.
B is correct, as vector addition shows if a student knows that gain of vertical speed in 1 s is 10 m/s. Choice a gives the horizontal or vertical speed, but not the resultant speed. Choice C has no credibility, and choice D indicates scalar addition of two 10 m/s vectors.
5. Relative to the ground, an airplane gains speed when it encounters wind from behind, and loses speed when it encounters wind head on. When it encounters wind at a right angle to the direction it is pointing, its speed relative to the ground below