Friction and Gravity

What is the best method to measure the amount of force needed to lift up a mug and a plate?

• Using a forcemeter

• Using a ruler
• Lift each item in your hand

• See their size

What do you use to measure force?

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Which surface will make the ball roll faster?

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What could be the problem that cause the car to skid?

• The highway surface is too rough

• The car wheels are rolling

• The car is not on the grass

• The surface of the tyres has become smooth

Where is the direction of the friction acts?

• opposite to the direction of motion
• in the same direction as the motion
• perpendicular to the direction of motion
• randomly in any direction

Gravity is ....

• a force that has no effect on objects
• a force that pulls the living things only down

• a force that pulls objects towards the center of the earth

• a force that repels objects from each other

Which one is the wrong statement about the girl whose playing slide?

• The friction between her body and slide slow her down

• The gravity pulls her downwards

• She will slide downward faster if the surface of the slide is smoother

• The gravity has no effects in this event

Liu jumps upward but soon Liu goes down. Why is it happen?

• The friction pulls him toward the Earth

• Liu is never jump actually

• Liu is bored staying in the air

• The gravity pulls him toward the Earth