All Chapters - Physics

Jane is using a 14 cm long screwdriver to assemble a bookcase. She applied a force of 45 N to rotate the screw 180 degrees. How much work did she do?

19.79 J

What tension do we need to put on the string of a 0.5 kg object, to spin it around in a 0.6 m radius circle, going 1.8 m/s?

2.7 N

You hang a flower basket using a horizontal pole, held to the wall with a bracket. If the basket weighs 0.7 kg and the pole is 40 cm long, how much torque is on the bracket?

2.74 Nm

Which of the following is a correct definition of rotational motion?

Where an object spins around an internal axis in a continuous way.

What happens when a spinning ice-skater with arms outstretched brings her arms close to her body?

She spins faster.

Why are perfectly elastic collision rare?

Some heat is usually generated

If it wasn't for friction or air resistance, what would happen to a spinning top?

It would keep spinning forever, because of Newton's 1st Law

What is the difference between kinematics and dynamics?

Kinematics studies motion without forces, dynamics includes forces.

What is one way you might increase the stability of an object?

Lower the center of gravity

A 4 kg object is moving at 3 m/s i-hat, and collides with a 3 kg object traveling at -10 m/s i-hat. They collide inelastically. What is the velocity of the combined mass immediately after the collisions.

-2.6 m/s

n a question, you're given the initial angular velocity, the angular acceleration, and the change in angle and asked to calculate how long it took to accelerate. Which equation should you use to solve this problem? Note: In the images below, w0 is the initial angular velocity, and w is the final angular velocity. This is another way of notating the same thing, which you may well see in problems and tests.)

0=w0t+1/2at2 - Weird 0

What is the definition of angular velocity?

he number of radians an object rotates by each second

Most translational quantities have a rotational equivalent. What is the translational equivalent of moment of inertia?

mass

Which best describes momentum?

mass in motion

An object moving in uniform circular motion has a constant _____, but a changing _____.

speed; velocity

What do we call the ability of an object to maintain its balance after being disturbed?

stability

When an object is in _____, tilting it will raise the height of its center of gravity, and it will return to its normal stable state after being tilted.

stable equilibrium

Which of the following is a full definition of uniform circular motion?

t is motion in a circle at a constant speed; this happens because of a centripetal force, a force pointing towards the center of a circle.

Which of the following is NOT one of the big 5 equations for rotational motion with a constant acceleration? Note: In the images below, w0 is the initial angular velocity, and w is the final angular velocity. This is another way of notating the same thing, which you may well see in problems and tests.)

v2=vo2+2ax

Which conservation law applies to elastic collisions, but NOT to inelastic collisions?

conservation of kinetic energy

Which of the following is the rotational version of Newton's 1st Law?

A spinning body will stay spinning, a non-spinning body won't start spinning, unless acted upon by an unbalanced torque.

What must be exerted an object for it to have momentum?

An external force

What is the difference between a system and an isolated system?

An isolated system cannot be affected by outside forces.

Which of the following is NOT an example of torque in the real-world?

Sliding furniture along the ground.

What happens when the direction of an object in circular motion changes, but the speed remains unchanged?

The acceleration changes.

The equation below represents which conservation law? Pitiot = Pitot Pi1+Pi 2 = Pf1 = Pf2 m1vi1 + m2vi2 = m1vf1 + m2vf2

Conservation of momentum

When a soccer player kicks a soccer ball, which type of collision usually occurs?

Elastic

What does it mean to say that momentum is?

There is no net change

What happens to two objects after they collide in an elastic collision?

They bounce off each other.

Why do the cannon and cannonball cancel out each others' momenta?

They have equal and opposite momenta

What is a collision?

Two objects coming in contact with each other

What is the difference between a scalar and a vector?

Vectors have a direction and scalars do not.

Which of the following is NOT a rotational quantity used in physics?

Force

n object is rotating at a rate of 5 radians per second. If it takes 3 seconds for the object to reduce its velocity to 1 radian per second, what is the angular acceleration?

- 1.33 radians per second per second

What is the momentum of a 10 kg object traveling at 10 m/s?

100 kgm/s

A person applied a work of 25 J to a tool during a period of 2 seconds. What power did the person exert over the tool?

12.5 watts

A disk was spinning at a speed of 2.5 radians/second and then its speed increased to 5.0 radians/second. If it takes the disk 4 seconds to speed up from 2.5 to 5.0, how far does it turn during this acceleration?

15 radians

A car of real 1500 kg, moves in a circle at 30 m/s. If the circle has a radius of 8 meters, what is the size of the frictional force that is moving the car in the circle?

168750 newtons

A ball on a string in uniform circular motion has a velocity of 8 meters per second, a mass of 2 kilograms, and the radius of the circle is 0.5 meters. What is the centripetal force keeping the ball in the circle?

256 N

A spinning top is spun at an angular velocity of 3 radians per second, by applying a torque of 10 newton-meters. How much power is being transferred to the spinning top?

30 watts.

A 6 kg mass moves at 4 m/s i-hat + 3 m/s j-hat. It collides inelastically with a 5 kg mass moving at 4 m/s i-hat. What is the momentum of the combined masses immediately after the collision?

4 m/s i-hat + 1.64 m/s j-hat

Calculate the moment of inertia using the following data. KE = 3,400 J Angular velocity = 2 rotations per second

43.06 kg m2

In a physics lab, a 10 kg mass is propelled at 6 m/s into a second 20 kg mass moving at 3 m/s. After they collide and bounce off each other, the 10 kg mass is moving at 2 m/s. Using the conservation of kinetic energy, find the velocity of the 20 kg mass after the collision.

5 m/s

f a force of 10 newtons is applied at a distance of 5 meters from a pivot point, what torque does this produce?

50 newton meters.

If an object has a mass of 10 kg and a velocity of 6 m/s to the left, what is its momentum?

60 kg*m/s to the left

If the initial angle of a turntable compared against an arbitrary line is 20 degrees, and half a second later it has rotated to 370 degrees, what is the angular velocity of the turntable?

700 degrees per second.

A ball weighing 13 kg goes around an object with a radius of 3 m at a speed of 4.5 m/s. What is the force of gravity that the object exerts on the ball?

87.75 N

Joshua is making some calculations for his science fair project. He observes a small car move in a circle and divides the angle of rotation by the time it took the car to reach that angle. What is Joshua calculating?

Angular velocity

Which equation represents the relationship between impulse and momentum?

Force * time interval = change in mass * velocity

Which type of collision results in objects that stick together or become permanently deformed?

Inelastic collision

A system is _____ if there are no external forces acting on the objects in the system.

Isolated

Why is increasing the time interval a safer way to land from a fall?

It decreases the amount of force

What is the equation for momentum?

Mass (kg) * Velocity (m/s)

An external force must act in order to change the _____ of a system.

Momentum

The equation shown in the image below is used to solve problems involving _____.

Momentum

What is conserved within any system?

Momentum

eff's car weighs 2000 lbs and is moving east at 20 km/hour. Jordan's car is twice as heavy, and is moving east at 10 km/hour. Whose car has more momentum?

Neither. Both cars have the same momentum.

Which best describes an elastic collision?

No permanent damage occurs

When friction acts on two billiard balls, are the balls part of an isolated system?

No, because friction is an external net force

If you push a heavy box across a room is it an isolated system?

No, because there is an unbalanced external force

How was it possible for the bike and the semi-truck to have the same momentum?

One had less mass but a greater velocity

In a general sense, what do we mean by conservation of angular momentum?

The angular momentum in a system is being preserved.

Which of the following is true for an object in stable equilibrium?

The center of gravity will raise when tilted

Which of the following is true for an object in neutral equilibrium?

The center of gravity will remain at the same height when tilted

What will occur when a force is applied to the center of an object?

The object will spin.

When you're whirling a ball on a string, what SPECIFIC force keeps it moving in a circle? (What force would you mark on a force diagram of the situation?)

The tension force.

If you are falling, which scenario will cause the greatest change in momentum when you land?

Your change in momentum is the same no matter what

What do we call a measurement of an object's ability to keep spinning?

angular momentum