Question

A B C D E 1. Six identical Physics books, each with mass 2.0 kg, are taken to the Moon. On the Moon, their combined mass is a) zero, b) 2.0 kg, c) 6.0 kg, d) 12 kg.

A B C D E 2. According to Newton's Law of Gravitation, if the distance between two bodies is doubled the attractive force between them is a) increased

by a factor of 2, b) decreased by a factor of 1/2, c) increased by a factor of 4, d) decreased by a factor of ¼

PROBLEMS, If your answer differs by a little bit in the last digit, remember that the answers here may have been rounded off

A B C D E 3.

An object weighs 20 newtons on Earth. What is its approximate mass? a) 2kg, b) 20g, c) 10kg , d) 196kg, e) 640kg

A B C D E 4. The kinetic energy of a body is correctly given by which of the following expressions? a) mv, b) 2mv^2, c) mv^2, d) (1/2)mv^2, e) (1/2)mv.

A B C D E 5. If the speed of a car is doubled, the work to stop the car changes by a factor of a) 4, b) 2, c) 1, d) 1/2, e) 1/4.

A B C D E 6. A ball is traveling at a constant speed of 5 m/s in a circle with a radius of 1.2 m. What is the centripetal acceleration of the ball in m/s^2)? a) 4.17, b) 6.2, c) 20.8, d) 60, e) none of the above.

Answer 1

1) The mass of an object remains constat everywhere.

hence, combined mass on the surface of moon = combined mas on earth = 6 x 2 = 12 kg

hence, corrct option is (d) 12 kg

2) the gravitational force is given by

F = G m₁ m₂ / r²

or, F ∝ 1/ r²

since, the gravitational force is inverslely proportional to the square of the distance

hence, after doubling the the distance the force will become one-fourth

hence, correct option is (d) decreased by a factor of ¼

3) mass = weight / acceleration du to gravity = 20 / 9.8 = 2.04 kg = 2 kg

hence, correct option is (a) 2kg

4) the kinetic energy is given by

K.E = 1/2 mv²

hence, correct option is (d) (1/2)mv^2

5) the work done to stop a car = kinetic energy of the car = 1/2 mv²

hence,  If the speed of a car is doubled, the kinetic energy becomes four times. Hence, the wok done becomes four times.

hence, correct option is (a) 4

6) given, speed, v = 5 m/s

radius, r = 1.2 m

centripetal acceleration, a_c = v²/r = 5²/ 1.2 = 25 / 1.2

hence, a_c = 20.8 m/s²

hence, correct option is (c) 20.8