Red force
Gives the two names of the force that pulls objects toward the Earth?
Gravity or Weight
What is the unit to measure forces, and its symbol?
Newton (N)
Give an example of how decreasing friction is helpful.
Oiling a machine or bike, waxing a snowboard, using a cart with wheels to move an object
g is the gravitational force field. What is its value on Earth? and its unit?
10 N/kg
When an object is at rest/stationary ... A-There are no forces acting on it. B-There are forces acting on it but these forces are balanced. C-There is just one force acting on it, gravity D-The forces acting on it are unbalanced
B-There are forces acting on it but these forces are balanced
What are the two different types of forces?
Contact and non-contact forces
Cars being driven on icy roads can have better traction if they have chains on their tires . Why?
Because chains increase the friction between the tires and the road.
Give the name of two forces that slow down moving objects?
Friction, drag forces, air resistance, water resistance
What is the upward force acting on an object as it falls through the air?
Air resistance or drag force
If equal and opposite forces cause no acceleration, they are said to be…
Balanced
What is the force that supports you when you float?
Upthrust or buoyancy
A ship floats because .....
The weight of the ship is balanced by upthrust/buoyancy of the water.
When an object falls, air resistance ...
acts in the opposite direction to the movement
As you ascend (go up) in an spacecraft and you are farther from the Earth's centre, what happens to your weight?
It decreases
What is the weight of a person who has a mass of 40 kg? Show your working.
weight = mass x g; weight = 40kg x 10 N/kg; weight = 400 N
Define Hooke’s law on a spring
The extension of the spring doubles when the force acting on it doubles.
Bungee cords can stretch. How do we call the amount that they stretch?
The extension
Snails produce mucus (slime) to help them move along the ground. How does the mucus help snails move?
Mucus reduces friction. It acts as a lubricant.
Three satellites are orbiting the Earth. The distance from Earth is 6,000 km for Satellite A; 10,000 km for Satellite B; and 35,800 km for Satellite C. Which one would Earth have the greatest attraction for? Explain why.
Satellite A because it’s the closest. The gravitational field strength is stronger on satellite A.
What effect do unbalanced forces have on an object’s motion?
Unbalanced forces change an object’s motion.
Explain the difference between weight and mass
Weight is a force so it is measured in Newtons. Mass is the amount of “stuff” something is made of. It is measured in kilograms (kg).
A cart is pulled to the right by a force of 15 N and to the left by a force of 20 N. What is the net force on the cart? in which direction?
The net force on the cart is 5N to the left
Gives an advantage (example) of friction?
It holds your feet on the ground while you walk; It allows cars to brake; Friction holds a nail in the wall/ceiling; It helps to hold a glass or grip a pencil.
On which planet of our solar system would you feel heaviest? Explain
The one which has the highest value of g (gravitational field strength): Jupiter
A girl stands still holding a racket on a tennis court. A ball is coming towards her. Which two forces are balanced?
Her weight and the reaction of the ground.