Dynamics

A car is accelerated by a constant resultant force of $300\text{ N}$ for $5.0\text{ s}$.
The variation with time of the velocity, in $\text{cm s}^{-1}$, of the car is shown.

What is the mass of the car?

Options

A   $13\text{ kg}$
B   $1000\text{ kg}$
C   $1300\text{ kg}$
D   $10\,000\text{ kg}$

What is a statement of the principle of conservation of momentum for a system?

Options

A   The total momentum and the total kinetic energy are always conserved.
B   The total momentum is conserved only in elastic collisions.
C   The total momentum is conserved provided that no external forces act.
D   The total momentum of each object in the system is the product of its mass and velocity.

Objects P and Q form an isolated system.
Object P has mass $6.0\text{ kg}$ and is moving at a speed of $3.0\text{ m s}^{-1}$.
Object Q has mass $2.0\text{ kg}$ and is moving at a speed of $4.2\text{ m s}^{-1}$ at an angle of $35^\circ$ to the path of P.

Objects P and Q collide and stick together.
What is the magnitude of the component of the final momentum of the combined objects in the original direction of P?

Options

A   $9.6\text{ kg m s}^{-1}$
B   $11\text{ kg m s}^{-1}$
C   $13\text{ kg m s}^{-1}$
D   $25\text{ kg m s}^{-1}$

An astronaut of mass $m$ in a spacecraft experiences a gravitational force $F = mg$ when stationary on the launchpad.
What is the gravitational force on the astronaut when the spacecraft is launched vertically upwards with an acceleration of $0.2g$?

Options

A   $1.2mg$
B   $mg$
C   $0.8mg$
D   $0$

A stationary nucleus has nucleon number $A$.
The nucleus decays by emitting a proton with speed $v$ to form a new nucleus with speed $u$. The new nucleus and the proton move away from one another in opposite directions.
Which equation gives $v$ in terms of $A$ and $u$?

Options

A   $v = \left(\frac{A}{4} - 1\right)u$
B   $v = (A - 1)u$
C   $v = Au$
D   $v = (A + 1)u$

What is always conserved in elastic collisions?

Options

A firework travels vertically upwards in air. Gases are pushed vertically downwards from the firework.

Several forces that act on the firework and gases are shown.

Which forces are a Newton’s third law pair?

Options

A   air resistance and force on gases
B   air resistance and thrust
C   force on gases and thrust
D   thrust and weight

Two blocks K and L slide towards each other along a horizontal frictionless surface.

The diagram shows the momentum of the two blocks just before they collide.

During the collision, the blocks are in contact with each other for a time of $0.084\text{ s}$.

After the collision, the blocks separate and block L moves back along its original path with a momentum of $0.12\text{ kg m s}^{-1}$.

What is the magnitude of the average force exerted on block L by block K during the collision?

Options

A   $3.1\text{ N}$
B   $4.0\text{ N}$
C   $6.9\text{ N}$
D   $7.1\text{ N}$

The momentum of a car of mass $m$ increases from $p_1$ to $p_2$.

What is the increase in the kinetic energy of the car?

Options

A   $\dfrac{(p_2^2 - p_1)^2}{2m}$
B   $\dfrac{(p_2 - p_1)^2}{2m}$
C   $\dfrac{p_2 - p_1}{2m}$
D   $\dfrac{p_1 - p_2}{2m}$

A solid object of mass $1.0\text{ kg}$ falls vertically downwards in a vacuum.

When the speed of the object is $60\text{ m s}^{-1}$, an additional constant force of $50\text{ N}$ suddenly starts to act vertically upwards on the object.

What is the speed of the object $2.0\text{ s}$ after the additional force starts to act?

Options

A   $20\text{ m s}^{-1}$
B   $40\text{ m s}^{-1}$
C   $80\text{ m s}^{-1}$
D   $100\text{ m s}^{-1}$