physics year 7

What is the formula for calculating work?

• Work = Mass × Acceleration

• Work = Force + Distance

• Work = Force × Distance × cos(θ)

• Work = Energy × Time

Define energy in your own words.

• Energy is a type of food.

• Energy is a form of matter.

• Energy is the ability to perform work or cause change.

• Energy is the total amount of heat in an object.

What is power in terms of work and time?

• Power = Work + Time

• Power = Time / Work

• Power = Work / Time

• Power = Work - Time

How do you calculate the efficiency of a machine?

• Efficiency (%) = (Input Energy / Output Energy) x 100

• Efficiency (%) = (Input Power / Output Power) x 100

• Efficiency (%) = (Output Work / Input Work) x 100

• Efficiency (%) = (Output Energy / Input Energy) x 100

If a machine does 100 J of work and uses 120 J of energy, what is its efficiency?

• 75%

• 83.33%

• 90%

• 100%

What is the velocity ratio of a machine?

• The velocity ratio of a machine is the ratio of the distance moved by the effort to the distance moved by the load.

• The velocity ratio is the time taken by the load to the time taken by the effort.

• The velocity ratio is the speed of the load divided by the speed of the effort.

• The velocity ratio is the weight of the load compared to the weight of the effort.

If a machine has a velocity ratio of 4, what does that mean?

• The machine multiplies the input distance by 4 to achieve the output distance.

• The machine multiplies the input force by 4 to achieve the output force.

• The machine has a velocity ratio of 4, meaning it reduces the output distance by 4 times.

• The machine divides the input distance by 4 to achieve the output distance.

Explain the difference between input work and output work.

• Input work is the energy supplied to a system, while output work is the energy produced by the system.

• Input work refers to the total energy of a system, while output work is the energy that cannot be measured.

• Input work is the energy produced by a system, while output work is the energy supplied to the system.

• Input work is the energy lost by a system, while output work is the energy consumed by the system.

What is a simple machine? Give two examples.

• A bicycle

• A hammer and nail

• Examples of simple machines are a lever and a pulley.

• A wheel and axle

How does friction affect the efficiency of a machine?

• Friction decreases the efficiency of a machine by causing energy loss and opposing motion.

• Friction increases the efficiency of a machine by enhancing motion.

• Friction only affects the appearance of a machine, not its efficiency.

• Friction has no effect on the efficiency of a machine.