Paper 1 Dynamics Drills

Q1

Newton’s second law in its most general H2 form states that resultant external force equals

A. mass times speed.
B. rate of change of momentum.
C. change in kinetic energy per unit distance.
D. impulse.

Q2

A constant resultant force of $12\mathrm{N}$ acts on a $3.0\mathrm{kg}$ object. Its acceleration is

A. $0.25\mathrm{m}{\mathrm{s}}^{-2}$
B. $4.0\mathrm{m}{\mathrm{s}}^{-2}$
C. $9.0\mathrm{m}{\mathrm{s}}^{-2}$
D. $36\mathrm{m}{\mathrm{s}}^{-2}$

Q3

An object moves at constant velocity in a straight line. The resultant force on it is

A. zero.
B. in the direction of velocity.
C. opposite to velocity.
D. equal to its weight.

Q4

Which pair of forces is a Newton’s third-law pair?

A. weight of a book and normal force on the book
B. tension up on a hanging mass and weight down on the mass
C. force of a bat on a ball and force of the ball on the bat
D. friction and air resistance on the same moving object

Q5

The momentum of a $0.20\mathrm{kg}$ ball moving at $15\mathrm{m}{\mathrm{s}}^{-1}$ is

A. $0.013\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$
B. $3.0\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$
C. $15.2\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$
D. $75\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$

Q6

Impulse is equal to

A. force divided by time.
B. change in momentum.
C. kinetic energy.
D. momentum divided by mass.

Q7

The area under a force-time graph gives

A. acceleration.
B. impulse.
C. power.
D. displacement.

Q8

When can the total momentum of a system be conserved during a collision?

A. only if kinetic energy is conserved
B. only if the collision is elastic
C. when resultant external impulse is zero or negligible
D. when the objects have equal masses

Q9

A $0.50\mathrm{kg}$ trolley moving at $2.0\mathrm{m}{\mathrm{s}}^{-1}$ collides and sticks to a stationary $1.50\mathrm{kg}$ trolley. Their common speed is

A. $0.50\mathrm{m}{\mathrm{s}}^{-1}$
B. $1.0\mathrm{m}{\mathrm{s}}^{-1}$
C. $2.0\mathrm{m}{\mathrm{s}}^{-1}$
D. $4.0\mathrm{m}{\mathrm{s}}^{-1}$

Q10

In a perfectly elastic one-dimensional collision, which quantities are conserved for the colliding system?

A. momentum only
B. kinetic energy only
C. both momentum and kinetic energy
D. neither momentum nor kinetic energy

Q11

A lift accelerates upward. The normal contact force on a passenger is

A. less than the passenger’s weight.
B. equal to the passenger’s weight.
C. greater than the passenger’s weight.
D. zero.

Q12

A passenger feels apparently weightless in a freely falling lift because

A. gravity is zero.
B. the passenger’s weight is zero.
C. the normal contact force is zero.
D. momentum is not conserved.

Q13

Two connected blocks accelerate together on a smooth horizontal surface. If the two blocks are treated as one system, the internal tension between them

A. must be included twice.
B. cancels and need not appear in the external-force equation.
C. becomes the resultant external force.
D. is equal to zero.

Q14

A resultant force acts in the opposite direction to an object’s velocity. The object

A. must be moving in a circle.
B. slows down initially.
C. speeds up initially.
D. has zero momentum.

Q15

The SI unit $\mathrm{N}\mathrm{s}$ is equivalent to

A. $\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-1}$
B. $\mathrm{kg}\mathrm{m}{\mathrm{s}}^{-2}$
C. $\mathrm{kg}{\mathrm{m}}^2{\mathrm{s}}^{-2}$
D. $\mathrm{kg}{\mathrm{s}}^{-1}$

Q16

For a non-constant force during a collision, the average force is found from

A. $\Delta p/\Delta t$.
B. $\Delta t/\Delta p$.
C. $m{v}^2/r$.
D. $mg\Delta h$.

Q17

In an inelastic collision,

A. momentum is not conserved.
B. kinetic energy is not conserved.
C. the objects must stick together.
D. total energy is destroyed.

Q18

Which statement about third-law forces is correct?

A. They act on the same body.
B. They may have different magnitudes if masses differ.
C. They are equal and opposite forces of the same interaction type.
D. They cancel in the free-body diagram of one object.

Q19

A body of mass $m$ moving with velocity $\vec{v}$ has momentum

A. $m|\vec{v}|$ only, a scalar.
B. $m\vec{v}$, a vector.
C. $\vec{v}/m$, a vector.
D. $m\vec{a}$, a vector.

Q20

A ball bounces from a wall and reverses direction. The magnitude of its momentum change is large because

A. momentum is scalar.
B. final and initial momentum are in opposite directions.
C. kinetic energy must increase.
D. wall force is zero.