# Force

Instructions: answer the questions, check them carefully, and when you are sure they are all right, press submit. The number of correct answers will be displayed.

Question 1: Why is it that when we apply a constant force to a box on a rough floor it does not accelerate according to F = m.a., but moves at a constant velocity?

Question 2: An aeroplane's engines are applying constant force. Why does it reach a certain cruising speed and stop accelerating?

Question 3: A bigger athlete has more strength in his legs, so has more force. But a smaller athlete, who can exert a smaller force from his legs, can accelerate faster because he has less mass. This principle is due to Newton's:

Question 4: When a basketball player jumps, he first bends his knees then pushes down. This is because he understands Newton's:

Question 5: When we hurt our hands punching a punching bag, this is an example of:

Question 6: A boy pushes a 10-kg box with 200N force. If the friction acting on the box is 100N, what is the acceleration on the box?

Question 7: A car accelerates at 15 m/s2. The resultant force on the vehicle is 15 kN. What is the mass of the car?

Question 8: What force is needed to move a 12-kg box across a table at an acceleration of 1 m/s2, if the friction force is 4.5 N?

Question 9: A boy sees 60kg when he stands on scales on Earth. What would be his weight on the Moon?

Question 10: A man sees 85kg when he stands on scales on Earth. What would be his mass on the Moon?

Question 11: What is the value of N which will just overcome the static friction as shown?

Question 12: Which of these is a consequence of Newton's First Law of Motion?