Free Force and Motion MCQs with Answers

• A. Joule
• B. Watt
• C. Newton
• D. Pascal

Explanation: The SI unit of force is the newton (N), defined as the force that accelerates a one-kilogram mass at one metre per second squared.

• A. force equals mass times velocity
• B. force equals the rate of change of momentum
• C. force equals mass times distance
• D. force equals momentum times time

Explanation: The general statement is that the net force equals the rate of change of momentum, which reduces to F equal to ma only when the mass is…

• A. a net force acting on it in the direction of motion
• B. zero net force acting on it
• C. a net force acting opposite to its motion
• D. an increasing acceleration

Explanation: Uniform velocity means zero acceleration, and by Newton's second law zero acceleration requires zero net force.

• A. 0.2 m s-2
• B. 5 m s-2
• C. 16 m s-2
• D. 80 m s-2

Explanation: From F equal to ma, the acceleration is 20 divided by 4, which is 5 m s-2.

• A. act on the same body and cancel out
• B. act on different bodies and therefore never cancel
• C. are unequal in magnitude
• D. act in the same direction

Explanation: The pair is equal in magnitude and opposite in direction but acts on two different bodies, which is why they cannot cancel each other and…

• A. 30 degrees
• B. 45 degrees
• C. 60 degrees
• D. 90 degrees

Explanation: Range is proportional to sine of twice the launch angle, which is largest when twice the angle is 90 degrees, so the angle itself is 45…

• A. zero in every direction
• B. horizontal only, with the vertical component zero
• C. vertical only
• D. equal to the launch velocity

Explanation: Gravity acts only vertically, so the horizontal component of velocity is unchanged throughout the flight while the vertical component…

• A. Speed
• B. Distance
• C. Displacement
• D. Time

Explanation: Displacement has both magnitude and direction, whereas distance records only how far was travelled with no direction attached.

• A. N s-1
• B. kg m s-1
• C. kg m s-2
• D. N m

Explanation: Momentum is mass times velocity, so its unit is kilogram metre per second.

• A. 0.5 m s-1
• B. 1 m s-1
• C. 1.5 m s-1
• D. 2 m s-1

Explanation: Momentum is conserved, so the initial momentum of 2 times 3, which is 6 kg m s-1, is shared by the combined mass of 6 kg, giving a…

• A. Kinetic energy
• B. Mass alone
• C. Velocity of each body
• D. Potential energy

Explanation: An elastic collision is defined by the conservation of kinetic energy as well as momentum, and collisions between gas molecules are…

• A. 40 m
• B. 80 m
• C. 160 m
• D. 320 m

Explanation: With uniform acceleration from rest the average velocity is half the final velocity, which is 10 m s-1, and over 8 s that gives 80 m.

• A. acceleration
• B. displacement
• C. force
• D. momentum

Explanation: Multiplying velocity by time gives displacement, so the area enclosed between the curve and the time axis is the displacement travelled.

• A. the acceleration produced by a force
• B. inertia, the tendency of a body to resist a change in its state of motion
• C. action and reaction pairs
• D. the conservation of energy

Explanation: A body continues at rest or in uniform motion in a straight line unless a resultant force acts, so the law defines what a force actually…

• A. 4 m per second squared
• B. 100 m per second squared
• C. 0.25 m per second squared
• D. 25 m per second squared

Explanation: From F equals ma, the acceleration is 20 divided by 5, giving 4 m per second squared in the direction of the resultant force.

• A. act on the same body and therefore cancel
• B. act on two different bodies, so they never cancel each other
• C. are unequal in magnitude
• D. act in the same direction

Explanation: Action and reaction are equal and opposite but act on different objects, which is why a book on a table is held up by the table's push…

• A. the rate of change of momentum
• B. momentum multiplied by time
• C. mass divided by acceleration
• D. work divided by distance only

Explanation: F equals ma is the special case of this for constant mass; the momentum form is more general and handles situations such as a rocket…

• A. its change in kinetic energy
• B. its change in momentum
• C. the work done on it
• D. its mass times its velocity

Explanation: Impulse is force multiplied by the time for which it acts, and it equals the change in momentum, which is why airbags and crumple zones…

• A. always increases
• B. is conserved, whatever type of collision occurs
• C. is conserved only in elastic collisions
• D. is zero

Explanation: Momentum conservation follows from Newton's third law and holds in every collision and explosion provided no external force acts, whether…

• A. bounce apart with no loss of kinetic energy
• B. stick together and move with a common velocity, losing some kinetic energy
• C. conserve kinetic energy but not momentum
• D. come to rest

Explanation: Momentum is still conserved, so the common velocity follows from the total momentum divided by the total mass, but some kinetic energy is…