Gravity and weight

A teacher wants to measure the specific latent heat of ice.

The diagram shows the equipment the teacher uses.

Here are some steps in the method for this experiment. The steps are not in the correct order.

Write numbers in the boxes next to each step to show the correct order. One is already done for you.

In one set of results 0.006 kg of ice melts.

Calculate the weight of the ice that melts.

Gravitational field strength = 10 N / kg

Use the equation: gravitational force = mass × gravitational field strength

The heater is turned on for 150 seconds.

The power of the heater is 15 W.

Calculate the energy transferred by the heater.

Use the equation: energy transferred = power × time

In another set of results 0.015 kg of ice melts.

The energy transferred by the heater is 5010 J.

Calculate the specific latent heat of ice.

Use the Equation Sheet.

Specific latent heat of ice =........ J / kg

An astronaut has a mass of 70 kg on Earth.

The mass of the Moon is smaller than the mass of the Earth.

Which row describes the astronaut’s mass and weight on the Moon compared to their mass and

A teacher measures the specific latent heat of ice using this method:

• Pour water at 30 °C into a beaker.

• Add the ice cube to the beaker of water.

• Measure the final temperature of the water after the ice cube melts.

Here are the first set of results from the experiment.

Starting temperature of ice cube = 0 °C Mass of water = 0.2 kg Starting temperature of water = 30 °C Final temperature of water = 14 °C The specific heat capacity of water = 4200 J / kg °C

Calculate the change in thermal energy of the water.

Use the Equation Sheet.

Give your answer to 2 significant figures.

The ice must be dried with a paper towel before starting the experiment.

Suggest why.

Describe how the terms specific latent heat and specific heat capacity are different.

The teacher then measures the density of an ice cube.

This is the method they use:

• Measure the mass of the ice cube.

• Place the ice cube in a measuring cylinder containing water.

• Measure the increase in volume of the water after the water has settled.

• Divide the mass by the increase in volume to measure density.

The teacher’s method does not give an accurate value for the density of ice.

Suggest why.

Suggest a change to the method which would give a more accurate value for the density of ice.

The mass of an astronaut is 80 kg.

Calculate the weight of the astronaut on the Moon.

Use the equation: gravitational force = mass × gravitational field strength

The gravitational field strength on the Moon is 1.6 N / kg.

A 50 N

B 128 N

C 800 N

D 1280 N

Planets X and Z are the same size.

• The gravitational field strength on planet X is 12 N / kg.

• Planet X has a mass of 1 × 10²⁵ kg.

• Planet Z has a mass of 4 × 10²⁵ kg.

What is the gravitational field strength on planet Z ? Use the Data Sheet.

A 0.75 N / kg

B 3 N / kg

C 12 N / kg

D 48 N / kg

Each planet, A – D, has the same diameter (width).

Which planet has the largest gravitational field strength?

A student carries out an experiment to calculate the spring constant of a spring.

Here are the student’s results.

Calculate the force when the mass is 200 g.

Use the equation: gravitational force = mass × gravitational field strength

Assume gravitational field strength = 10 N / kg.

Calculate the spring constant when the mass is 500 g.

Use the equation: force exerted by a spring = extension × spring constant

Give your answer to the nearest whole number.

Spring constant =........ N / m

Calculate the mean value of the spring constant.

Use the values in the table from 100 g to 400 g only.

Mean spring constant =........ N / m

The teacher says that calculating the mean is a poor method to find the spring constant, even though the student’s calculations are correct.

Describe a better way to find the spring constant using the student’s measurements.

Explain in words what is meant by power.

A weightlifter lifts a 200 pound (200 lb) mass.

1 lb = 0.454 kg.

Calculate the weight of the mass in Newtons.

Use the equation: gravitational force = mass × gravitational field strength

Gravitational field strength = 10 N / kg.

This is some data for a weightlifter.

Weight lifted = 620 N Height of the lift = 1.6 m Time taken to complete lift = 4.0 s

Calculate the power generated by the weightlifter.

Use the equations: work done = force × distance power = work done / time

A student measures the acceleration of a trolley on a horizontal surface.

Fig. 15.1 is a diagram of her experiment.

The weight of the masses accelerates the trolley.

Define the term weight.

Show that the weight of a 100 g mass is 1 N.

Friction can change the results of this experiment.

Suggest one way friction can be reduced.

The tall parts of the card on the trolley (U and V) pass through the light gate, as shown in Fig. 15.2.

The velocity of U is 0.5 m / s.

The velocity of V is 1.0 m / s.

Calculate the acceleration of the trolley.

Use the equation: (final velocity)² – (initial velocity)² = 2 acceleration distance

Acceleration =........ m / s²

When the trolley reaches the edge of the surface, it is moving at 1.2 m / s.

The mass of the trolley is 1.0 kg.

Calculate the kinetic energy of the trolley.

The student repeats the experiment with different masses.

This is a graph showing her results.

The student says, ‘The graph shows that the acceleration of the trolley is directly proportional to the force.’

Is the student correct?

Explain your answer.

Which statement about gravitational fields is correct?

A A spacecraft has a gravitational field that causes attraction.

B Gravitational fields are attractive and repulsive.

C Gravitational field strength is measured in newtons.

D The larger the mass the smaller the gravitational field.

On the Moon, a 10 kg mass has a weight of 16 N.

What is the gravitational field strength on the Moon?

A 1.6 N / kg

B 6.0 N / kg

C 26 N / kg

D 160 N / kg

Student A does an experiment to find out if force is related to acceleration.

Fig. 15.1 is a diagram of her experiment.

She hangs a 400 g mass over the pulley.

How can she work out the accelerating force on the trolley?

Use an equation to help explain your answer.

The tall parts of the card on the trolley labelled X and Y pass through the light gate, as shown in Fig. 15.2.

The light gate can measure:

• the time it takes for Y to go through

• the time it takes for X to go through

• the time between Y and X going through.

How can student A use the light gate and card to measure the acceleration of the trolley?

Use an equation to help explain your answer.

Describe one way this experiment could be improved.

* Student A records some measurements. She plots the data points and draws a line of best fit on the graph in Fig. 15.3.

Describe and explain what the results in Fig. 15.3 show. Comment on the validity of student A ’s results shown on the graph in Fig. 15.3.

You are not expected to include a calculation.

Student B does the same experiment.

Fig. 15.4 is a graph of her results.

Calculate the gradient of the graph in Fig. 15.4.

Gradient =........ per kg

Student B ’s graph in Fig. 15.4 can be described by an equation.

Write this equation in the form: y = mx + c

Use your answer to 15(e)(i) and student B ’s graph in Fig. 15.4 to help you.

What is the gravitational field strength on Earth?

A 1.0 N/kg

B 1.6 N/kg

C 10.0 N/kg

D 98.9 N/kg