Exercises Force
6N
1. There are 4 forces acting on an object such as shown on the figure.
5N
12N
a. Are the vertical forces in equilibrium?
b. Are the horizontal forces in equilibrium?
6N
c. Calculate the resultant of vertical and horizontal forces!
2. If the object in the above figure is initially in motion, explain how to maintain its motion with a
constant velocity!
3. Can we walk on the ground? Explain!
4. Why car need to change lubrication oil every 5000 km? Explain!
5. The mass of an object located on Earth is 120 kg. if the earth’s gravitational acceleration is 9.8 m/s2 and
the moon’s gravitational acceleration is 1/6
of the earth’s, then calculate the weight of the same object on the moon !
6. What acceleration will result when a 12 N net force applied to a 3 kg object and 6 kg object?
7. A net force of 16 N causes a mass to accelerate at a rate of 5 m/s2. Determine the mass !
8. How much force is needed to accelerate a 66 kg skier 1 m/s2 ?
9. What is the force on a 1000 kg elevator that is falling freely at 9.8 m/s2 ?
10. How much force is needed to accelerate a 1400 kilogram car 2 m/s2 ?
11. A car produces a 2000 N force. What is its acceleration if its mass is 2000 kg and the friction caused by
air resistance and the road’s surface is 1000 N?
12. Fill in the blank
13. Adi pushes a table to the right with a 200 N forces, while Budi pushes the same table with a 150 N
force in the same direction as Adi. The resultant of the two forces is . . . . N
14. pay attention to the following figure
Calculate the resultant force and direction !
15. when you get a ride on your friend’s bicycle, what happens when suddenly it starts to move forward?
16. When will the resultant force is equal to zero?
17. Why do you feel pain in your foot when you kick a table? Explain your answer using newton law’s
concept!
18. A stone is thrown to hit a wall. The result is that the wall is damaged and the stone flies away. Which
one has a greater contact force? Why is it so? Explain your answer using newton law’s concept!
19. What is newton’s opinion about the motion of an object? Explain your answer!
20. Write down two examples of newton’s 3rd law in daily life (don’t use the example in your note book!)
Exercises/Grade 8/Forces/January 2016
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