Physics 23-10-24

A car of mass 750kg has a horizontal driving force of 2.0kN acting on it. It has a forward horizontal acceleration of 2.0ms^–2.

What is the resistive force acting horizontally?

• 0.50kN

• 1.5kN

• 2.0kN

• 3.5kN

Which of the following is a statement of the principle of conservation of momentum?

• The momentum of an isolated system is constant

• In an elastic collision momentum is constant

• Momentum is the product of mass and velocity

• The force acting on a body is proportional to its rate of change of momentum

A 2.0kg mass travelling at 3.0ms^–1 on a frictionless surface collides head-on with a stationary 1.0kg mass. The masses stick together on impact.

• 3.0J

• Zero

• 2.0J

• 2.4J

• B

• A

• C

• D

A hinged trapdoor is held closed in a horizontal position by a cable.

Three forces act on a trapdoor: The weight W of the door, the tension T in the cable and the force H at the hinge.

Which list gives the three forces in increasing order of magnitude?

• W, H, T

• H, T, W

• T, H, W

• W, T, H

A wind turbine has blades that sweep an area of 2000m². It converts the power available in the wind to electrical power with an efficiency of 50%.

What is the electrical power generated if the wind speed is 10ms^–1? (The density of air is 1.3kg m^–3)

• 130kW

• 650kW

• 1300kW

• 2600kW

• B

• A

• C

• D

• A

• B

• C

• D

• A

• B

• C

• D

All external forces on a body cancel out.

Which statement must be correct?

• The momentum of the body remains unchanged

• The body does not move

• The speed of the body remains unchanged

• The total energy (kinetic and potential) of the body remains unchanged