1.2 Motion (3)
Resources |
Revision Questions |
Physics
Login to see all questions
Click on a question to view the answer
1.
A speed-time graph for a car is provided below.
(b) Using the speed-time graph, determine whether the car is moving with constant speed, accelerating, or decelerating. Explain your answer.
Answer: The car is moving with constant speed.
Reasoning: The speed-time graph shows a horizontal line, indicating that the speed of the car is not changing with time. A constant speed is represented by a horizontal line on a speed-time graph. Acceleration would be shown by a line with a positive slope, and deceleration by a line with a negative slope.
2.
An object is dropped from the top of a building. Assuming air resistance is negligible, state, with a reason, why the object’s velocity increases at a constant rate as it falls.
The object's velocity increases at a constant rate because the only force acting on it is gravity. According to Newton's Second Law of Motion (F = ma), a net force causes acceleration. Since the gravitational force (F = mg) is approximately constant near the Earth's surface, and mass (m) is also constant, the acceleration (a = F/m = mg/m = g) is also constant. A constant acceleration means a constant rate of change in velocity.
3.
A car accelerates from rest to a speed of 20 m/s in 5 seconds. Calculate the acceleration of the car. Show your working.
Given:
- Initial velocity (u) = 0 m/s
- Final velocity (v) = 20 m/s
- Time (t) = 5 s
Equation: a = Δv / Δt
Calculation:
a = (20 m/s - 0 m/s) / 5 s = 4 m/s2
Answer: The acceleration of the car is 4 m/s2.