EmSAT EmSAT Physics 1 — Questions and Answers
Question 1: What is Newton's second law of motion?
- F = mv
- F = ma (Correct answer)
- F = m/a
- F = a/m
Correct answer: F = ma
Newton's second law states that force equals mass times acceleration: F = ma. It describes how the motion of an object changes when a net force acts on it.
Question 2: A car travels 120 km in 2 hours. What is its average speed?
- 240 km/h
- 60 km/h (Correct answer)
- 30 km/h
- 120 km/h
Correct answer: 60 km/h
Average speed = distance ÷ time = 120 km ÷ 2 h = 60 km/h.
Question 3: What is the unit of force in the SI system?
- Joule
- Watt
- Newton (Correct answer)
- Pascal
Correct answer: Newton
The SI unit of force is the Newton (N), defined as the force needed to accelerate a 1 kg mass at 1 m/s². It is named after Isaac Newton.
Question 4: An object is in free fall. What is its acceleration? (ignore air resistance)
- 0 m/s²
- 5 m/s²
- 9.8 m/s² (Correct answer)
- 10.8 m/s²
Correct answer: 9.8 m/s²
On Earth, the acceleration due to gravity is approximately 9.8 m/s² downward. All objects in free fall (ignoring air resistance) accelerate at this rate.
Question 5: What does the area under a velocity-time graph represent?
- Speed
- Acceleration
- Distance (Correct answer)
- Force
Correct answer: Distance
The area under a velocity-time graph represents the displacement (distance traveled). This is derived from the relationship: distance = velocity × time.
Question 6: Which of Newton's laws explains why a seat belt protects you in a crash?
- First law (inertia) (Correct answer)
- Second law (F=ma)
- Third law (action-reaction)
- Law of gravitation
Correct answer: First law (inertia)
Newton's first law states that objects in motion stay in motion unless acted upon by a net force. In a crash, your body continues moving forward due to inertia; the seat belt provides the force to stop you.
EmSAT EmSAT Physics 1
What is Newton's second law of motion?