Unit 2 - Mechanics Flashcards
Rifle B is fired and the bullet emerges with a smaller horizontal velocity than the bullet from rifle A. Explain why the horizontal distance travelled by bullet B will be less than bullet A. (3)
- Vertical motion is independent of horizontal motion
- So bullet A and B in air for same time
- Horizontal acceleration is zero, so distance is proportional to horizontal speed
Explain, with reference to energy, why the velocity of a diver is independent of his mass if air resistance is insignificant. (3)
- Potential energy is transferred to kinetic energy
- mgΔh = 0.5mv^2
- Mass cancels, so independent
A snowboarder is moving at a constant velocity down a slope. State and explain what happens to the gravitational potential energy lost. (3)
- Gravitational potential energy transferred to thermal energy
- Through friction
- No increase in kinetic energy as GPE converted to heat. So no acceleration/ constant velocity
State the principle of moments. (3)
- Sum of…
- Clockwise moments = anticlockwise moments
- For a system in equilibrium
State two vector quantities. (1)
Velocity/ acceleration/ displacement/ force
State two scalar quantities. (1)
Speed/ distance/ mass
Define the moment of a force about a point. (2)
- Force x perpendicular distance
* Between line of action of force and the point
State the principle of moments. (2)
- Clockwise moments = anticlockwise moments
* For a system in equilibrium
Explain why using an inclined plane rather than free fall would produce data which is valid when investigating the motion of a falling object. (2)
(Any two)
• Free fall is too quick
• Galileo had no accurate method to time free fall
• Reduces air resistance or drag
Describe the energy changes that take place from the moment a cannonball leaves a cannon on a castle until just before it hits the water. Include the effects of air resistance. (2)
- Potential energy transferred to kinetic energy
* Kinetic energy into thermal due to air resistance
