12th grade forces and motion

Question 1

A stone is thrown horizontally at 15 m/s from a cliff 4.9 m high. How far from the base of the cliff does it land, in m? (g = 9.8 m/s²; ignore air resistance)

Answer m

Question 2

Who first published the law of universal gravitation?

• A. Albert Einstein
• B. Johannes Kepler
• C. Galileo Galilei
• D. Isaac Newton

Question 3

Calculate the gravitational field strength at the surface of Mars, in N/kg. Mass = 6.42 × 10²³ kg, radius = 3.39 × 10⁶ m, G = 6.67 × 10⁻¹¹ N m²/kg². (g = G M ÷ r²; give 1 decimal place)

Answer N/kg

Question 4

In which direction does the centripetal force on an object moving in a circle act?

• A. there is no force
• B. towards the centre of the circle
• C. forwards along the path
• D. outwards, away from the centre

Question 5

A 800 kg object moves in a circle of radius 50 m at 5 m/s. What centripetal force is needed, in N? (F = m v² ÷ r)

Answer N

Question 6

Friction between the tyres and the road provides 3200 N of centripetal force for a 1000 kg car on a bend of radius 20 m. What is the car's speed, in m/s?

Answer m/s

Question 7

A ball is kicked horizontally off a cliff 19.6 m high. Ignoring air resistance, how long does it take to reach the beach below, in s? (g = 9.8 m/s²; give 2 decimal places)

Answer s

Question 8

One ball is dropped and another is fired horizontally from the same height at the same moment. Which lands first (no air resistance)?

• A. The fired ball
• B. The dropped ball
• C. They land at the same time
• D. It depends on their masses

Question 9

One of two masses is multiplied by 4 and the distance stays the same. By what factor does the gravitational force change? (F = G m₁ m₂ ÷ r²)

Answer 

Question 10

A stone is thrown horizontally at 10 m/s from a cliff 4.9 m high. How far from the base of the cliff does it land, in m? (g = 9.8 m/s²; ignore air resistance)

Answer m

Question 11

Why is the value of g slightly smaller at the top of a high mountain?

• A. It is colder
• B. There is less air
• C. Mountains have less mass
• D. You are slightly further from Earth's centre

Question 12

Calculate the gravitational field strength at the surface of Mars, in N/kg. Mass = 6.42 × 10²³ kg, radius = 3.39 × 10⁶ m, G = 6.67 × 10⁻¹¹ N m²/kg². (g = G M ÷ r²; give 1 decimal place)

Answer N/kg

Question 13

In which direction does the centripetal force on an object moving in a circle act?

• A. towards the centre of the circle
• B. outwards, away from the centre
• C. there is no force
• D. forwards along the path

Question 14

A 1 kg object moves in a circle of radius 50 m at 15 m/s. What centripetal force is needed, in N? (F = m v² ÷ r)

Answer N

Question 15

Friction between the tyres and the road provides 6750 N of centripetal force for a 1200 kg car on a bend of radius 40 m. What is the car's speed, in m/s?

Answer m/s

Question 16

A ball is kicked horizontally off a cliff 19.6 m high. Ignoring air resistance, how long does it take to reach the beach below, in s? (g = 9.8 m/s²; give 2 decimal places)

Answer s