Test 1 - Newton's Laws of Motion

A train travels 6 meters in the first second of travel, 6 meters again during the next second of travel, and 6 meters again during the third second. Its acceleration is……..?

0 m/s²

A car starts from rest and after 7 seconds it is moving at 42 m/s. What is the car’s average acceleration?

6 m/s²

When a basketball player jumps to make a shot, once the feet are off the floor, the jumper’s acceleration……

Is g; no more no less.

Suppose a car is moving in a straight line and steadily decreases its speed. It moves from 55 km/h to 45 km/h the first second and from 45 km/h to 35 km/h the next second. What is the car’s acceleration?

-10 km/(h x s)

A ball is thrown straight up. At the top of its path its instantaneous speed is?

0 m/s

On Earth, a freely falling object starts from rest. After falling for 6 seconds, it will have a speed of about….?

60 m/s

A 15-N force and a 45-N force act on an object in opposite directions. What is the net force on the object?

30 N

A girl whose weight is 500 N hangs from the middle of a bar supported b two vertical strands of rope. What is the tension in each strand?

250 N

What is needed to describe a vector quantity?

Both magnitude and direction.

A scalar quantity has….?

Only magnitude.

The law of inertia states that an object….

Will continue moving in a straight line unless an outside force acts on it.

An object following a straight-line path at constant speed….

Has zero acceleration.

Compared to its mass on Earth, the mass of a 10-kg object on the moon is….

The same.

Which has more mass, a kilogram of feathers or a kilogram of iron?

Neither—they both have the same mass.

T or F - An object in static equilibrium is in a state of no motion.

True

T or F - Friction refers to the force between two surfaces that are sliding past each other.

True

T or F - If you were to slide a hockey puck across a frictionless ice rink, there must be a horizontal force on it to keep it in motion.

False

T or F - The weight of an object is equal to the force of gravity on that object.

True

T or F - An astronaut weighs the same on Earth as on the moon.

False

Problem: A jet on an aircraft carrier can be launched from 0 to 40 m/s in 2 seconds. What is the acceleration of the jet?

20 m/s²

Problem: A skateboarder starting from rest accelerates down a ramp at 2 m/s² for 3s. What is the final speed of the skateboarder?

6 meters

The acceleration produced by a net force on an object is….

Inversely proportional to the mass of the object, directly proportional to the magnitude of the net force, and in the same direction as the net force.

When an object reaches terminal velocity its acceleration is….

0 m/s²

When a woman stands with two feet on a scale, the scale reads 280 N. When she lifts one foot, the scale reads….

280 N

Suppose the force of friction on a sliding object is 25 N. The force needed to maintain a constant velocity is….?

25 N

A book weighs 4 N. When held at rest in your hands the net force on the book is….

0 N

A girl pulls on a 10-kg wagon with a constant force of 20 N. What is the wagon’s acceleration?

(20 N / 10 KG) = 2 m/s²

A tennis ball and a solid steel ball with the same diameter are dropped at the same time. In the absence of air resistance, which ball has the greater acceleration.

They both have the same acceleration.

If the force acting on a cart doubles, what happens to the cart’s acceleration?

It doubles.

Suppose a cart is being moved by a force. If suddenly a load is dumped into the cart so that the cart’s mass doubles, what happens to the cart’s acceleration?

It halves.

A tow truck exerts a force of 2000 N on a car, accelerating it at 1/m/s/s. What is the mass of the car?

2000 kg

You pull horizontally on a 50-kg crate with a force of 450 N and the friction force on the crate is 250 N. The acceleration of the crate is?

4 m/s²

How much force is needed to accelerate a 4.0-kg physics book at a rate of 2.0 m/s²?

8 N

Whenever an object exerts a force on another object, the second object exerts a force of the same magnitude , but in the opposite direction to that of the first object.

Always true.

An unfortunate bug splatters against the windshield of a moving car. Compared to the force of the car on the bug, the force on the car is….

The same.

An unfortunate bug splatters against the windshield of a moving car. Compared to the deceleration of the car, the deceleration of the bug is….

larger

Two people pull on a rope in a tug-of-war. Each pulls with a 400 N of force. What is the tension in the rope?

400 N

Suppose you accidentally drive into a tree which of the following correctly describes the interaction between your car and the tree?

The car and the tree mutually exert equal and opposite force on each other.

T or F - The combination of all the forces that act on an object is called the net force.

True

T or F - Excluding the force due to air pressure, there is only one force acting on a book lying at rest on a table top.

False

T or F - The net force on an object falling at terminal velocity is zero.

True

T or F - Whenever on object exerts a force on another object, the second object always exerts a force back on the first object.

True

T or F - A rocket ship is pushed forward by gases that are forced out the back of the ship.

True

T or F - The length of a vector represents its magnitude.

False

T or F - The orientation of a vector shows its direction.

True

T or F - The acceleration of an object is inversely proportional to the net force acting on it.

False