Physics U2 - Force

The amount of force required to keep a 6-kg object moving with a constant velocity of 2 m/s is ___ N

a force is NOT required to keep an object in motion

Newton's second law

acceleration of an object is directly proportional to the force put on it

Newton's first law

an object at rest will remain at rest, an object in motion will remain in motion, unless acted upon by an external force

If a moose were chasing you through the woods, its enormous mass would be very threatening. But if you zigzagged, then its great mass would be to your advantage. Explain why.

because his mass is greater than you, its inertia would interfere with its running because it would resist more

Why do you fall into your sibling in the car when you turn?

car is turning but your body is still going straight

T/F: A ball is moving upwards and rightwards towards its peak. The ball experiences a force that is directed upwards and rightwards

false

T/F: A cannonball is shot from a cannon at a very high speed. The force of the explosion will be experienced by the cannonball for several seconds (or at least a little while)

false

T/F: A force is required to keep an object moving in a given direction

false

T/F: A high speed object (say, moving at 200mi/hr) will possess measurably more mass than the same object when at rest

false

T/F: A high-speed object (say, moving at 200mi/hr) will weigh less than the same object when at rest

false

T/F: A rightward moving object must be experiencing (or at least usually does experience) a rightward force

false

T/F: All objects weigh the same amount when placed in a vacuum, regardless of their mass

false

T/F: An upward moving object must be experiencing (or at least usually does experience) an upward force

false

T/F: If a person throws a ball with his hand, then the force of the hand upon the ball is experienced by the ball for at least a little while after the ball leaves the hand

false

T/F: If an object is at rest, then there are no forces acting upon the object

false

T/F: Objects do NOT weigh anything when placed in a vacuum

false

T/F: Weight is the result of air pressure exerted upon an object

false

Newton's third law

for every action, there is an equal and opposite reaction

More mass = ...

more inertia

Would Shirley be able to conduct the brick experiment in outer space far from the influence of significant gravitational forces? Why or why not? Explain.

no. because there is no force in outer space, they would go at the same speed

Inertia

resisting a change in motion

Inertia can best be described as...

the tendency of any object to resist change and keep doing whatever its doing

T/F: A free-falling object still has weight

true

T/F: An object weighs less on the moon than it does on the Earth

true

T/F: The mass of an object on the moon is the same as its mass on the Earth

true

T/F: Weight is measured in pounds; mass is measured in Newtons

true

Two bricks are resting on the edge of the lab table. Shirley Sheshort stand on her own toes and spots the two bricks. She acquires an intense desire to know which of the two bricks are most massive. Since Shirley is vertically challenged, she is unable to reach high enough and lift the bricks; she can however reach high enough to give the bricks a push. Discuss how the process of pushing the bricks will allow Shirley to determine which of the two bricks is most massive. What difference will Shirley observe and how can this observation lead to the necessary conclusion?

- heavier brick will drop first because is has more mass than the lighter brick - the bricks will fall and the heavier one will hit the ground first