# Worksheet: Newton's Second Law of Motion

In this worksheet, we will practice applying Newton's second law of motion, F = ma, to find the acceleration caused by forces that act in various directions.

**Q5: **

An object of mass 7.5 kg has a force applied to it that pulls eastward with a magnitude of 50 N and another applied to it that pulls westward with a magnitude of 150 N. What is the westward acceleration of the object? Give your answer to one decimal place.

**Q7: **

An object accelerates at 4 m/s^{2} while a force of
20 N is applied to it. What is the mass of the object?

**Q8: **

A skateboarder of mass
50 kg
stands on a skateboard of mass
1.5 kg,
close to the wall of a building.
The skateboarder stands with one foot on the board and uses the other foot to push away from the wall.
The skateboard accelerates away from the wall at
4.66 m/s^{2}.
With how much force did the skateboarder push against the wall?
Give your answer to the nearest newton.

**Q9: **

A sheet of paper is at rest on a desk next to an open
window. A short gust of wind blows in through the window and the sheet of paper
is blown in the direction of the gust. The paper accelerates in
the direction of the air flow at 0.33 m/s^{2}. The air that hits the
paper applies a force of 0.001 N to it. Find the mass of the paper to the
nearest whole number of grams.

**Q10: **

A bolt that has a mass of 125 g is placed on a horizontally aligned crossbow and the crossbow’s string is tightened. The crossbow’s string is released when the crossbow trigger is pulled, and the recoiling string hits the bolt and applies a force of 45 N to it. The bolt flies away from the crossbow. What rate of acceleration does the bolt have in the direction of the push from the string?

**Q11: **

A car of mass 630 kg is moving at 9 m/s. The car brakes to slow down to a speed of 3 m/s in a distance of 6 m. What average force does the car apply throughout its braking? Give the answer to the nearest newton.

**Q12: **

A swimmer of mass 48 kg uses her legs to push herself away from a swimming pool wall, applying a force of 280 N. The water that the swimmer accelerates through applies 160 N of force in the opposite direction to that in which she accelerates. What is the swimmer’s acceleration through the water?

**Q13: **

An object with a mass of 22 kg has a force applied to it. The graph shows the change in the object’s velocity while the force is applied. How much force is applied to the object? Answer to the nearest newton.

**Q14: **

An object of mass 75 kg has a force applied to it. The graph shows the change in the object’s velocity while the force is applied. How much force is applied to the object? Give your answer to the nearest newton.

**Q15: **

Which of the following formulas correctly relates force, mass, and acceleration?

- A
- B
- C
- D
- E

**Q16: **

An object with a mass of 35 kg has a force applied to it. The graph shows the changes in the object’s velocity while the force is applied.

How much force is applied to the object from to ?

How much force is applied to the object from to ?

How much force is applied to the object from to ?

**Q17: **

An object has forces of 30 N and 55 N applied to it. The
forces act in opposite directions to each other, as shown in the diagram. The
object accelerates to the left at 0.5 m/s^{2}. What is the mass of the
object?

**Q18: **

A hammer of mass 1.75 kg hits a nail.
Before it hits the nail, the hammer is moving horizontally. When the hammer hits the nail,
it decelerates to rest at 0.75 m/s^{2}. How much force does the hammer apply to the nail? Give your
answer to one decimal place.

**Q19: **

A car of mass 400 kg has broken down. The car has two occupants,
each of mass 50 kg, and they agree that the car’s engine may start
to work again if the car can be made to move at a certain speed. One occupant stays in the car and tries to get the engine going
and the other occupant pushes the car from behind, as shown in the diagram. The push applied to the car provides a force of 850 N,
and the car accelerates in the direction of the push at 0.267 m/s^{2}.
How much force, to the nearest newton, does the friction of the car wheels with the ground apply?

**Q20: **

A ball has a mass of 250 g. The ball is kicked and this applies a force of 15 N to the ball, as shown in the diagram. How much does the ball accelerate by in the direction of the kick?

**Q21: **

A speck of dust with a mass of 0.25 g in deep space very far from any other objects is at rest. In another completely different part of deep space that is also very far from any other objects, a tiny ice crystal with a mass of 0.75 g moves at a constant speed of 25 m/s.

What is the speck of dust’s rate of acceleration?

What net force acts on the speck of dust?

What is the ice crystal’s rate of acceleration?

What net force acts on the ice crystal?