### How does it work?

Option 1: Just fill in the form with your homework question, and someone will respond shortly with an answer.

Option 2: Take a photo (or link) of your question, and email or text it to us.

### Like us? ## Horizontal Launch off a Cliff

Q: An object is launched horizontally off a cliff with a velocity of 14 m/s. a) How long will it be in the air for? b) How far, horizontally, will the ball move before hitting the ground?

A: The keys to this question is that horizontal velocity is constant, and initially the vertical velocity . . . → Read More: Horizontal Launch off a Cliff

## Airplane with Tailwind and Headwind

Q: An airplane flew 3 hours with a 40 mph head wind. The return trip with a tail wind of the same speed took 2 hours. Find the speed of the plane in still air.

A: When you have a headwind, you have to subtract the wind’s speed from the . . . → Read More: Airplane with Tailwind and Headwind

## Vectors

Q: What is the difference between a scalar and a vector quantity?

A: A scalar quantity is one that is described only by a magnitude. A vector quantity is described by both a magnitude AND a direction.

If I say, “I walked 4 kilometres to the store” 4 kilometres is a scalar quantity, because . . . → Read More: Vectors

## Ball thrown vertically upwards

Q: A tennis ball is thrown vertically upward with an initial velocity of +6.7 m/s. What will the ball’s velocity be when it returns to its starting point? The acceleration of gravity is 9.81 m/s^2.

A:

Its velocity will be – 6.7 m/s.

This is true for anything that is thrown vertically upwards. Look . . . → Read More: Ball thrown vertically upwards

## Kinematics Equations

Q: What are the kinematics equations?

Where = displacement = initial velocity = final velocity = acceleration = time

These are very useful, and you will use them many times before you are finished Physics 11. It would definitely help to memorize . . . → Read More: Kinematics Equations

## Vertical Motion of a Rocket

Q: A rocket moves upward, starting from rest with an acceleration of 27.2 m/s2 for 3.49 s. It runs out of fuel at the end of the 3.49 s, but does not stop. How high does it rise above the ground?

A: Okay the rocket’s moving up with an acceleration of +27.2m/s^2 for a . . . → Read More: Vertical Motion of a Rocket

## Tips to Remember for Kinematics and Projectile Questions

Some things you should know for projectiles (note that you haven’t done anything with angles yet, so you can ignore the sine and cosine parts):

The vertical and horizontal components are independent of each other. The vertical velocity is usually Vy = V*sin(ϴ) horizontal velocity is usually Vx = V*cos(ϴ), where V is the . . . → Read More: Tips to Remember for Kinematics and Projectile Questions

## Cart Collision in 1-Dimension

Q: Two carts with masses of 4.6 kg and 3.5 kg move toward each other on a frictionless track with speeds of 5.7 m/s and 4.5 m/s, respectively. The carts stick together after colliding head-on. Find their final speed.

A: m1 = 4.6 kg m2 = 3.5 kg v1 = 5.7 m/s (to the . . . → Read More: Cart Collision in 1-Dimension

## Kinetic energy of racing car

Q: A racing car has a mass of 1780 kg. The acceleration of gravity is 9.8 m/s^2. What is its kinetic energy if it has a speed of 103 km/h?

A: First note that kinetic energy can be denoted as KE or E_k[\latex]= 728550 J E_k[\latex] = 7.3×10^5 J

Gravity doesn’t affect the kinetic . . . → Read More: Kinetic energy of racing car

## Scooter and Bicycle, when will they meet?

Q: At 8:00am Dave leaves his home on his scooter, traveling east at 18 mph. At the same time and 80 mile away, Cathy leaves her home on her bicycle, traveling west toward Dave at 14 mph. At what time will they meet?

A: You know that D=VT, where D=distance, V=velocity (speed) and T . . . → Read More: Scooter and Bicycle, when will they meet?